FORMALDEHYDE AS A DISINFECTANT. BY ALVAH H. DOTY, M. D., HEALTH OFFICES OF THE POBT OF NEW YORK. BEPBINTED FROM THB Keto Yorfc JMeKfcal journal for October 16, 1897. Reprinted from the New York Medical Journal for October 16, 1897. FORMALDEHYDE AS A DISINFECTANT. By ALVAH H. DOTY, M. D„ HEALTH OFFICER OF THE PORT OF NEW YORK. It is safe to assume that no disinfectant which has been brought to the notice of the profession at any time has been more thoroughly and scientifically inves- tigated than formaldehyde gas. This is undoubtedly due to the fact that it comes to us when the germ theory of disease has been fully confirmed and accepted, and numerous bacteriological laboratories thoroughly equipped for experimental work in this direction are found throughout the civilized world. Agents which are believed to have germicidal powers now receive the most exhaustive investigation and their value or worth- lessness is decided. This is in marked contrast to the knowledge which we formerly possessed of these agents, particularly as to the gaseous disinfectants. Twenty years ago, before the value of steam as a disinfectant was fully appreciated, sulphurous-acid gas, or sulphur dioxide (SO2), was universally employed both by the profession and the laity. The range of its employment was very great, as it was used for the dis- Copyright, 1897, by D. Appleton and Company. 2 FORMALDEHYDE AS A DISINFECTANT. infection of ships, houses, etc., almost to the total ex- clusion of all other agents; in fact, it may be said that sulphur dioxide is the oldest disinfectant known, hav- ing been used in the time of Hippocrates and recom- mended by him. During this long period, in which SO2 reigned supreme, it had no competitor of any note. Chlorine gas, which at one time was regarded as equally valuable with sulphur, even if not more valuable, has practically dropped into obscurity. Admitting that sulphur dioxide is a very valuable agent for this pur- pose, it is well known that in some instances its use is impracticable, as it destroys or bleaches certain fabrics and renders them unfit for use. Steam, now regarded as the most valuable disinfectant which we possess, has practically taken the place of the dioxide in public dis- infection and wherever it can be used. Steam, however, can not be employed for the disinfection of houses, and the expense of the apparatus which is necessary for its practical application at present confines its use to quar- antine stations, health departments, hospitals, etc. Even when it is available, certain fabrics can not be treated by steam without injury or destruction; therefore the necessity of a disinfectant which at times can be used in place of steam or sulphur has been urgently felt. In 1868 Professor A. W. Hofmann, a German chemist, discovered that in heating a platinum spiral over the flame of an ordinary laboratory lamp burning methyl, or wood, alcohol a gas was produced, to which the name of formaldehyde was given. In 1888 A. Trillat, a French investigator, observed that the addi- tion of a small amount of this gas to urine prevented or retarded decomposition. This was followed by fur- ther investigation, the details of which he published in FORMALDEHYDE AS A DISINFECTANT. 3 1891. Subsequently, in 1892, he gave to the French Academy of Sciences the results of his work on the germicidal properties of formaldehyde. Since that pe- riod the interest in this agent has increased, and during the past two years its disinfecting properties have been carefully and thoroughly investigated both at home and abroad. The original and simple lamp of Hofmann has been gradually improved, until to-day we are in possession of lamps of large capacity and capable of generating suffi- cient gas to disinfect a spacious apartment. It is be- yond the scope of this article to give a detailed descrip- tion of the improvement made in this apparatus more than to say that the first lamp for the generation of formaldehyde gas sufficient for general disinfection was probably devised by Professor F. C. Robinson, of Bow- doin College, Maine, and shown by him at the meeting of the American Public Health Association held in Buffalo in 1896. Since that time numerous lamps of practically the same construction have been presented to the public. The details of Professor Robinson's lamp, which may be taken as a representative of the rest, will be explained in another portion of this article. In order to ascertain the value of formaldehyde gas as a disinfectant, experimental work in this direction was begun at the New York Quarantine Station during the fall of last year and has been continued until the present time. It has been my aim to obtain results which are of practical value; not only to ascertain the germicidal power of this gas upon exposed surfaces, but to ascertain what penetration we may expect from it- this knowledge being essential to its proper applica- tion. Consequently, the micro-organisms used were not 4 FORMALDEHYDE AS A DISINFECTANT. only directly exposed to the gas, but were placed inside of sterilized blankets, newspapers, and other packages in a manner similar to the experiments with steam re- cently reported by me. In order to keep in the lines of quarantine work pathogenic organisms were used- viz., the cholera, anthrax, and diphtheria bacilli and the bacillus of the plague. The degree of virulence was kept at the highest point by the occasional inoculation of guinea-pigs and white mice. Controls were made in each experiment; portions of the same culture being placed in packages and kept outside of the room or receptacle used for the test. If the controls did not grow the experiment was not recorded. The value of the result thus obtained is beyond question, and it will be appreciated that the work was necessarily slow and arduous. The tests detailed in the tables which are presented in this article were confirmed by others of the same character. I therefore feel confident that the results presented prove the value of formaldehyde as a super- ficial disinfectant. The plague cultures used were from three sources: from the Hoagland Laboratory, Brook- lyn; from the Pasteur Institute in Paris, through the courtesy of Professor Metchnikoff; and a culture re- ceived from Professor Haffkine, of Bombay; so that there could be no doubt as to the identity of this organ- ism. It will be observed that in the experiment plague cultures of two different kinds are used. The propaga- tion and care of these germs were, as in the experi- ments made with steam, under the direction of Dr. C. B. Fitzpatrick, the bacteriologist in charge of the labora- tory at the New York Quarantine Station. The tests were made in the steam chamber and in FORMALDEHYDE AS A DISINFECTANT. 5 the steel formaldehyde tank or chamber on the disin- fecting steamer James W. Wadsworth; also in a room of a thousand cubic feet space made expressly for the purpose in the laboratory of this department. In the centre of the floor of this room is a spray nozzle con- nected with a tank in an adjoining apartment holding ammonia gas in a liquefied state under a pressure of three hundred and fifty pounds. As a result the for- maldehyde gas can at any moment be neutralized. This room, which is almost perfectly tight, I have used as a standard in the experimental work. At the present time formaldehyde gas for the pur- pose of disinfection may be derived from the follow- ing sources: 1. From a commercial product, known as formalde- hyde (formalin, formol), said to be a forty-per-cent, solution of formaldehyde gas in water. The exact method of its production is not explained by the manu- facturers. It occurs as a clear, colorless fluid, having a characteristic odor and very irritating to the mucous membranes of the eyes and respiratory tract. 2. From the combination of the above-described formaldehyde solution (formalin) and chloride of cal- cium placed in a closed receptacle or autoclave. By the application of heat, the gas contained in the autoclave is given off in a dry state and'conducted through a tube to the apartment to be disinfected. 3. The generation of formaldehyde gas by the oxi- dation of methyl or wood alcohol in the lamp already referred to. 4. By the heating of paraformaldehyde in the form of tablets (paraform). FORMALDEHYDE AS A DISINFECTANT. 6 Foemaldehyde Solution. A method of disinfecting with formaldehyde solu- tion (formalin), now seldom used, is to place in the apartment to be disinfected a large shallow pan, into which is poured the amount of solution regarded as ne- cessary for the purpose; the apartment is then closed for a certain period-generally twelve hours. As already stated, it is claimed that the formaldehyde solution (for- malin) is a forty-per-cent, solution of formaldehyde gas in water; therefore the efficiency of the disinfection with this agent depends upon the amount of gas liberated. Those who believed that the entire amount of gas held in solution would be released have been doomed to dis- appointment, as experience has shown that only a small portion of it is given off. This may be demonstrated by agitating the solution left in the pan after its re- moval from the room under disinfection, when the pres- ence of formaldehyde is fully appreciated. Besides, it will be seen that along the edges of the pan on the inside, or at the circumference of the fluid, is a white chalky or soapy deposit. This is known as paraformal- dehyde, and was formerly regarded as an inert product. It is now known to be polymerized formaldehyde, from which the gas can only be released by the aid of heat under certain conditions. Therefore, as it remains in the pan, its value as a disinfectant is practically noth- ing. Although the following tables show that this so- lution may be used as a disinfectant with good results, they will also show that it is an extravagant method of securing formaldehyde gas, inasmuch as a .large per- centage is not liberated and a considerable amount is changed to the solid form, which at the time is value- FORMALDEHYDE AS A DISINFECTANT. 7 less. So far as can be ascertained by experiment, the gas is given off slowly and with no degree of regularity, which are objectionable features, particularly where the disinfection is performed in a living apartment; here the room, which contains windows and doors, can not be made absolutely tight, and a certain amount of the gas escapes. In the experimental work with this method tests were made in an absolutely tight re- ceptacle-viz., the steel chamber (without heat) on the James W. Wadsworth, consisting of a space of about a hundred and fifteen cubic feet; another series was made in a room of a thousand cubic feet, already de- scribed as constructed for the purpose. The latter may be regarded as representing an apartment in a dwelling house, although the room in question is carefully sealed and almost air-tight. FIRST SERIES. Experiments made in air tight chamber. Formaldehyde solution (formalin) in shallow pan on floor of apparatus. Table No. 1. Character of test: Cultures of the following organisms rubbed in (thor- oughly saturating) different portions of a sterilized thick woolen blanket.* After the exposure small discs from the infected spots were cut out and placed in tubes containing bouillon. Amount of formaldehyde solution (formalin) used, eight ounces; exposure, twelve hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. * This may be regarded as a severe test in superficial disinfection, and will constantly be made use of in the work which follows. 8 FORMALDEHYDE AS A DISINFECTANT. Table No. 2. Character of test same as Table No. 1. Amount of formaldehyde solu- tion (formalin) used, eight ounces; time of exposure, six hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. Table No. 3. Character of test same as Table No. 1. Amount of formaldehyde solution (formalin) used, four ounces; time of exposure, twelve hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) Growth. Cholera (5) No growth. Table No. 4. This and the following experiment (Tables No. 4 and 5) were made, not only to ascertain what penetration could be obtained, but also to test the value of the vacuum. Linen discs soaked in the different cul- tures were placed inside of the packages enumerated below. In each instance the packages were wrapped as tightly as possible. As the formaldehyde solution (formalin) is conducted to the interior of the chamber through a small pipe from a tank overhead, a vacuum in this experiment was made before the formalin was introduced. In this way the air contained in the chamber and, as far as possible, in the packages was removed, thereby offering less resistance to the penetration of the formaldehyde gas. Amount of formaldehyde solution (formalin) used, one quart; time of exposure, twelve hours. Plague (1), injected disc inside sheet of paper and envelope N o growth. Plague (2), " " " single newspaper No growth. Plague (3), " " " newspaper (weight, one lb.). Growth. Plague (4), " " " blanket No growth. Plague (5), " " " trwel No growth. Diphtheria (6), " " " sheet of paper and envelope No growth. Diphtheria (7), " " " single newspaper No growth. Diphtheria (8), " " " newspaper (weight, one lb.). Growth. FORMALDEHYDE AS A DISINFECTANT 9 Diphtheria (9), infected disc inside blanket .' Growth. Diphtheria (10), " " " towel No growth. Anthrax (11), " " " sheet of paper and enve- lope No growth. Anthrax (12), " " " single newspaper No growth. Anthrax (13), ♦ " " " newspaper (weight, one pound) Growth. Anthrax (14), " " " blanket No growth. Anthrax (15), " " " towel No growth. Table No. 5. Character of test same as Table No. 4, but without vacuum. Amount of formaldehyde solution (formalin) used, one quart; time of expos- ure, twelve hours. Plague (1), infected disc inside single newspaper Growth. Plague (2), " " " newspaper (one pound)... Growth. Plague (3), " " " blanket No growth. Plague (4), " " " towel No growth. Diphtheria (5), " " " single newspaper Growth. Diphtheria (6), " " " newspaper (one pound)... Growth. Diphtheria (7), " " " blanket Tube broken. Diphtheria (8), " " " towel Tube broken. Anthrax (9), " " " single newspaper Growth. Anthrax (10), '' " " newspaper (one pound).. . Growth. Anthrax (11), " " " blanket No growth. Anthrax (12), " " " towel No growth. The effect of the vacuum is here noticeable. In the experiment noted in Table No. 4, it will be seen that penetration took place in a single newspaper, and no growth occurred when the discs were removed from these packages and placed in bouillon; whereas in Table No. 5, where a vacuum was not made, a growth occurred when discs taken from a single newspaper were treated in the same manner. 10 FORMALDEHYDE AS A DISINFECTANT. SECOND SERIES. Table No. 6. Character of test same as Table No. 1. Experiments made in room of one thousand cubic feet space; amount of formaldehyde solution used, one pint; exposure, six hours. Plague (I) Growth. Plague (2) ..... Growth. Anthrax (3) Growth. Diphtheria (4) Growth. Cholera (5) Growth. Character of test same as Table No. 1. Amount of formaldehyde solu- tion (formalin) used, one pint; time of exposure, twelve hours. Table No. 7. Plague (1) Growth. Plague (2) Growth. Anthrax (3) Growth. Diphtheria (4) No groyvth. Cholera (5) Growth. Character of test same as Table No. 8. Amount of formaldehyde solu- tion (formalin) used, three pints; time of exposure, twelve hours. Table No. 8. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. The above experiments would show that for general disinfection this is an extravagant, unsatisfactory, and unreliable method of obtaining formaldehyde gas, and should only be used when no other method is avail- able. When employed, at least three pints of the solu- tion should be used for each thousand cubic feet of space. Even this can not always be depended upon, as the gas is only partly given off, depending in a great measure upon the size and shape of the receptacle. Therefore the pans should be large and shallow in order that the surface of formalin exposed shall be as great as possible. FORMALDEHYDE AS A DISINFECTANT. 11 The Combination of Formaldehyde Solution (For- malin) and a Solution of Chloride of Calcium. What has just been said as to the impracticability of securing the gas from the formaldehyde solution (formalin) in the manner above described was fully appreciated by Trillat, to whom we are indebted for the discovery of a method by which we are enabled to rapidly remove from the solution all the gas there- in contained. This investigator found that in adding to the formaldehyde solution a ten- to thirty-per- cent. solution of a neutral salt, preferably chloride of calcium, and placing the mixture in a closed receptacle and applying heat, all the gas contained in the mixture was rapidly given off in a comparatively dry state with- out the formation of paraformaldehyde. The apparatus (autoclave) which he devised for the purpose consists of a copper receptacle, silvered on the inside to prevent the action of the formaldehyde, which would in time affect the exposed copper. The receptacle has a capacity of about three or four quarts and stands on a tripod, allow- ing sufficient space for a lamp underneath. The top, or cover (which can be entirely removed), is securely fastened to the apparatus by turn-buckles. The auto- clave is supplied with a pressure gauge and has an es- cape pipe of about a sixteenth of an inch inside diam- eter, which conducts the gas from the autoclave through a keyhole or any small opening into the apartment to be disinfected. This pipe connects with an angle valve which regulates the escape of formaldehyde from the autoclave. The necessary amount of the mixture above referred to having been poured into the recep- tacle, the cover is tightly clamped, the lamp under- 12 FORMALDEHYDE AS A DISINFECTANT. neath the apparatus lighted, and the valve on the escape pipe closed until a temperature of 135° C. is reached; at this time there is an inside pressure of probably thirty pounds; the valve is then opened and the formaldehyde allowed to escape into the apartment under disinfec- tion. If the temperature does not exceed 135° C., the escaping gas contains but little moisture. This is re- garded by Trillat as particularly desirable, although moisture does not, so far as I can ascertain, interfere materially with the disinfecting qualities of the gas. However, upon delicate hangings, etc., the moisture does not have a desirable effect. Usually, after the valve is opened, the gas from a mixture containing one pint of the formaldehyde solution (formalin) will be dis- charged in about thirty minutes. When the autoclave is opened more or less fluid is found. If the tempera- ture has been raised about 135° C. the amount will de- pend on the volume of steam which has been given off with the gas. If the temperature is too high, and the operation is continued too long, nothing may be found in the receptacle but the chloride of calcium. With- out fluid in the autoclave, the heat is very apt to injure the metal. These details are carefully explained by the instrument makers. It must not be forgotten that con- siderable pressure in the operation is essential, and that the instrument should be of the very best construction; otherwise accidents may happen. After the experi- mental work at this station had proved the value of for- maldehyde gas as a disinfectant, I constructed on board the disinfecting boat James W. Wadsworth a circular steel chamber, or tank, having a capacity of two hun- dred and fifty cubic feet and being well braced in order to stand a vacuum (Fig. 1); to secure the latter a steam FORMALDEHYDE AS A DISINFECTANT. 13 exhauster was added. The chamber is fitted with a coil of pipe inside to secure heat, if at any time it is deemed advisable. It has in addition a fresh-air inlet pipe, Fig. 1. by which a current of fresh air may be drawn through the tank. The interior of this apparatus is fitted with 14 FORMALDEHYDE AS A DISINFECTANT. trays made of galvanized iron wire, upon which are carefully laid the articles to be disinfected. These may be put into the tank either through an opening on the Fig. 2. deck of the boat, or at the opening on the front of the tank. The latter is closed by a door which is hinged to a circular rim on the apparatus, containing a rub- FORMALDEHYDE AS A DISINFECTANT. 15 ber gasket, in order that the tank may be made air- tight. The door is fastened by turn-buckles. The auto- clave rests on a stand on the left and connected with the tank by a one-sixteenth-inch brass discharge pipe, which conducts the gas to the interior of the chamber, where disinfection is to be performed. Fig. 1 shows the cham- ber open, with the autoclave to the left, resting on a shelf. Fig. 2 shows the chamber closed. The material treated is, as a rule, that which can not be subjected to steam, and consists of silk, laces, leather goods, etc. The special advantages of this chamber are, first, the removal by the steam exhauster of the air in the chamber and in the material to be disinfected, thus allowing greater and quicker penetration by the formal- dehyde and performing the disinfection in a shorter time; second, the chamber being made air-tight, the material to be treated is affected by the entire volume of gas. The experiments with this method of disinfection were made in the formaldehyde chamber just described, and also in a room having a space of one thousand cubic feet. FIRST SERIES. Formaldehyde chamber. Table No. 9. Character of test: Infected discs were placed inside of packages made of small blankets and sheets of paper and envelopes. Amount of formaldehyde solution (formalin) contained in mixture, one pint; exposure, four hours. Cholera (1), infected disc inside of blanket No growth. Cholera (2), " " " •" paper and envelope.... No growth. Plague (3), " " " " blanket No growth. Plague (4), " " " " paper and envelope. ... No growth. Diphtheria (5), " " " " blanket.,..,.,., No growth. 16 FORMALDEHYDE AS A DISINFECTANT. Diphtheria (6), infected disc inside of paper and envelope. . No growth. Anthrax (7), " " " " blanket No growth. Anthrax (8), " " " " paper and envelope.. No growth Table No. 10. Character of test: Infected discs placed inside paper and envelopes as follows: Amount of formaldehyde solution (formalin) contained in mixture, one pint; exposure, four hours. Anthrax (1), inside single sheet of paper and envelope, ordi- narily sealed No growth. Anthrax (2), inside single sheet of paper and envelope, all seams extra gummed No growth. Anthrax (3), inside three sheets of paper and envelope, ordi- narily sealed No growth. Anthrax (4), inside three sheets of paper and envelope, all seams extra gummed No growth. Diphtheria (5), inside single sheet of paper and envelope, or- dinarily sealed No growth. Diphtheria (6), inside single sheet of paper and envelope, all seams extra gummed No growth. Diphtheria (7), inside three sheets of paper and envelope, ordinarily sealed No growth. Diphtheria (8), inside three sheets of paper and envelope, all seams extra gummed No growth. Character of test same as Table No. 1. Amount of formaldehyde solu- tion (formalin) contained in mixture, eight ounces; time of expos- ure, twelve hours. Table No. 11. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. Table No. 12. Character of test similar to above (table) Amount of formaldehyde solution (formalin) contained in mixture, eight ounces; exposure, six hours. Plague (1), infected disc inside of blanket No growth. Plague (2), " " " " " Growth. FORMALDEHYDE AS A DISINFECTANT 17 Anthrax (3), infected disc inside of blanket Growth. Diphtheria (4), " " " " " Growth. Cholera (5), " " " " " No growth. Table No. 13. Character of test same as Table No. 1. Amount of formaldehyde solu- tion (formalin) contained in mixture, four ounces; exposure, six hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. Table No. 14. Character of test same as Table No. 1. Amount of formaldehyde solu- tion (formalin) contained in mixture, four ounces; exposure, four hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5). No growth. Table No. 15. Character of test same as Table No. 1. Amount of formaldehyde solu- tion (formalin) contained in mixture, two ounces ; time of exposure, twelve hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. In the above series of experiments a vacuum was not made, as it was desired to ascertain the value of an air- tight apartment. It is safe to assume that with the addition to the vacuum the results just given would be made doubly certain. It is seen that the formaldehyde gas released from two ounces of formaldehyde solution (formalin) in the mixture placed in the autoclave will be sufficient for superficial disinfection in' an air-tight 18 FORMALDEHYDE AS A DISINFECTANT. chamber the capacity of which is two hundred and fifty cubic feet, provided there is an exposure of twelve hours. This result will generally be secured with an ex- posure of but six hours. It must be remembered, how- ever, that no other articles but the infected blanket were in the chamber. The experiments in Tables Nos. 9 and 10 were practically tests for penetration, as it relates to the disinfection of mail, etc., and show that with a pint of formalin in the mixture letters can be disin- fected in four hours. SECOND SERIES. The second series of experiments with this method of disinfection were made in a room containing one thousand cubic feet of space, as follows: Table No. 16. Character of test: The infected discs were placed inside of paper and envelope, in pockets of coat and on blanket. Amount of formalde- hyde solution (formalin) in m xture, one pint; time of exposure, four hours. Cholera (1), infected disc in pocket of coat No growth. Cholera (2), " " " " " " No growth. Cholera (3), " " on blanket No growth. Cholera (4), " " " sheet of paper and envelope. No growth. Plague (5), " " in pocket of coat No growth. Plague (6), " " " " " " No growth. Plague (7), " "on blanket Growth. Plague (8), " " " sheet of paper and envelope . No growth. Diphtheria (9), " " " pocket of coat No growth. Diphtheria (10), " " " " " " No growth. Diphtheria (11), " " " on blanket No growth. Diphtheria (12), " " " in sheet of paper and envelope No growth. Anthrax (13), " " " pocket of coat No growth. Anthrax (14), " " " " " " No growth. Anthrax (15), " " on blanket No growth. Anthrax (16), " " in sheet of paper and envelope. . No growth. FORMALDEHYDE AS A DISINFECTANT. 19 Table No. 17. Character of test: The infected discs were placed inside the following articles. Amount of formaldehyde solution (formalin) contained in mixture, one pint; time of exposure, fifteen hours. Plague (1), infected disc inside sheet of paper and envelope No growth. Plague (2), " " " single newspaper No growth. Plague (3), " " " newspaper (one pound).. . . Growth. Plague (4), " " " blanket No growth. Plague (5), " " " towel No growth. Diphtheria (6), " " " sheet of paper and envelope No growth. Diphtheria (7), " " " single newspaper Growth. Diphtheria (8), " " " newspaper (one pound)... . Growth. Diphtheria (9), " " " blanket No growth. Diphtheria (10), " " " towel No growth. Anthrax (11), " " " sheet of paper and envelope No growth. Anthrax (12), " " " single newspaper Growth. Anthrax (13), " " " newspaper (one pound).... Growth. Anthrax (14), " " " blanket No growth. Table No. 18. Character of test similar to Table No. 17. Amount of formaldehyde solution (formalin) contained in mixture, one pint; exposure, fifteen hours. Plague (1), infected disc inside sheet of paper and envelope No growth. Plague (2), " " " single newspaper Growth. Plague (3), " " " newspaper (one pound). . . . Growth. Plague (4), " " " blanket No growth. Plague (5), " " " towel No growth. Diphtheria (6), " " " sheet of paper and envelope No growth. Diphtheria (7), " " " single newspaper No growth. Diphtheria (8), " " " newspaper (one pound).... Growth. Diphtheria (9), " " " blanket No growth. Diphtheria (10), " " " towel Growth. Anthrax (11), " " " sheet of paper and envelope No growth. Anthrax (12), " " " single newspaper Growth. Anthrax (13), " " " newspaper (one pound).. .. Growth. Anthrax (14), " " " blanket No growth. Anthrax (15), " " " towel Growth. 20 FORMALDEHYDE AS A DISINFECTANT. Character of test: The infected discs were placed in a sterilized cotton envelope, and pinned on blanket and placed in pockets of coat. Amount of formaldehyde solution (formalin) contained in mixture, one pint; exposure, twelve hours. Cholera (1), infected disc on blanket No growth. Cholera (2), " " in coat pocket No growth. Plague (3), " " on blanket No growth. Plague (4), " " in coat pocket No growth. Plague (5), " " on blanket No growth. Plague (6), " " in coat pocket No growth. Anthrax (7), " " on blanket No growth. Anthrax (8), " " in coat pocket No growth. Diphtheria (9), " " on blanket No growth. Diphtheria (10), " " in coat pocket No growth. Table No. 19. In this same test discs were placed inside packages made of small pieces, of woolen blankets. Cholera (1), infected discs inside pieces of woolen blankets. No growth. Anthrax (2), " " " " " " No growth. Diphtheria (3), " " " " " " .... No growth. Plague (4), " " " " " " No growth. Table No. 20. Character of test same as Table No. 19. Amount of formaldehyde solution (formalin) used in mixture, one pint; time of exposure, four hours. Cholera (1), infected disc in pocket of coat No growth. Cholera (2), " " " " " " No growth. Cholera (3), " " on blanket.. No growth. Cholera (4), " " inside sheet of paper and envelope No growth. Plague (5), " " in pocket of coat No growth. Plague (6), " " " " " " No growth. Plague (7), " " on blanket Growth. Plague (8), " sheet of paper and envelope No growth. Diphtheria (9), " " in pocket of coat No growth. Diphtheria (10), " " " " " " No growth. Diphtheria (11), " " " blanket No growth. Diphtheria (12), " " " sheet of paper and envelope .. No growth. FORMALDEHYDE AS A DISINFECTANT 21 Anthrax (13), infected disc in pocket of coat No growth. Anthrax (14), " " " " " " No growth. Anthrax (15), " " "blanket No growth. Anthrax (16), " " " sheet of paper and envelope. . No growth. Table No. 21. Character of test same as Table No. 1. Amount of formaldehyde solution (formalin) contained in mixture, one pint; time of ex- posure, six hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. Table No. 22. Character of test: Infected discs placed inside cotton envelopes and pinned to blanket. Amount of formaldehyde solution (formalin) contained in mixture, eight ounces; time of exposure, twelve and a half hours. Plague (1), discs in sterilized cotton envelope pinned on blanket No growth. Plague (2), discs in sterilized cotton envelope pinned on blanket No growth. Anthrax (3), discs in sterilized cotton envelope pinned on blanket No growth. Diphtheria (4), discs in sterilized cotton envelope pinned on blanket No growth. Cholera (5), discs in sterilized cotton envelope pinned on blanket No growth. Character of test same as Table No. 1. Amount of formaldehyde solution (formalin) contained in mixture, eight ounces; time of exposure, twelve hours. Table No. 23. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. 22 FORMALDEHYDE AS A DISINFECTANT. Table No. 24. Character of test same as Table No. 1. Amount of formaldehyde solu- tion (formalin) contained in mixture, eight ounces ; time of ex- posure, twelve hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. Same experiment. Plague (1), infected discs inside sheet of paper and envelope. No growth. Plague (2), " " " " " " " " No growth. Anthrax (3) " " " " " " " " No growth. Diphtheria (4), " " " " " " " No growth. Cholera (5), " " " " " " " " No growth. Character of test same as Table No. 1. Amount of formaldehyde solution (formalin) contained in mixture, eight ounces; time of exposure, six hours. Table No. 25. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. It requires very little consideration to appreciate the superiority of the method just described. Tables 16, 17, 18, 19, and 20 not only show the value of formal- dehyde gas as a superficial disinfectant, but also that some penetration is usually secured, inasmuch as in these tests it penetrated paper and envelope, newspa- pers, blankets, towels, ets.; however, in room disinfec- tion its action in this respect can not always be depend- ed upon. A safe test for the value of this agent as a superficial disinfectant is its action on heavy sterilized woolen blankets, where cultures of the different organ- isms have been thoroughly rubbed into and through the fibre, as described in Table No. 1. An examina- FORMALDEHYDE AS A DISINFECTANT. 23 tion of Tables Nos. 22, 23, and 24, where this charac- ter of test was followed, would show that a mixture containing eight ounces of the formaldehyde solution, or formalin, is sufficient, when used in the Trillat appa- ratus, to disinfect a tightly closed room having a space of one thousand cubic feet, with an exposure of twelve hours. An exposure of six hours (see Table 25) is usual- ly sufficient, but can not always be depended upon. The formaldehyde solution (formalin) used in the test above described contained about thirty-one per cent, of gas, as shown by the analyses made by Dr. Lederle. The Generation of Formaldehyde Gas by the Oxidation of Methyl Alcohol in Lamp. As already stated, the simple lamp of Hofmann has to-day been replaced by lamps of different designs for the generation of formaldehyde gas from methyl alco- hol. These are not only practical, but are of suffi- cient size to disinfect apartments of considerable cubic space. The lamp suggested by Professor Robinson may be taken as a type of this method of generating the gas, inasmuch as it is simple and effective. In construc- tion it is similar to a student's lamp, having an up- right shaft supporting on one side the reservoir and on the other the pan which holds the alcohol escap- ing from the reservoir through a small tube. The pan, which is about eight inches in diameter and two inches in height, is covered by a movable cylinder ten inches high; the upper two or three inches being made cone shape, having an opening at the top of three inches. About midway in this cylinder is a diaphragm consist- ing of a disc made of platinized asbestos, perforated. In the cylinder above referred to are numerous openings. 24 FORMALDEHYDE AS A DISINFECTANT. These are important, inasmuch as it is necessary to admit just enough air to maintain the proper com- bustion. In preparing the lamp for use, the amount of methyl alcohol required for the disinfection is placed in the reservoir, and through the small tube it reaches the pan on the opposite side. The mechanism is so adjusted that the alcohol fills the pan to a height just above the opening of the tube, which lies on the floor of the pan. A match is now carefully applied to the exposed alcohol and the cylinder put in place over the flame. It is kept in this position for a minute or less, until the asbestos disc is thoroughly heated; the cylin- der is then quickly removed, and the flame extinguished by holding a cover over the pan. The cylinder is again put in place. The heat from the disc vaporizes the alcohol and oxidation ensues, and, as a result, the as- bestos disc becomes red hot. Formaldehyde is now dis- charged from the lamp and the room is closed. It fre- quently occurs that the disc is not sufficiently heated in the first instance. For this reason the lamp should not be left until the disc is seen to be heated red. The following experiments with the formaldehyde lamp were made in a room of one thousand cubic feet of space: Table No. 26. Character of test: Infected discs were placed inside the packages enumerated below. Amount of alcohol used, one quart; time of exposure, twelve hours. Anthrax (1), infected disc inside of towel No growth. Anthrax (2), " " " envelope and paper No growth. Anthrax (3), " " " newspaper No growth. Cholera (4), " " " towel No growth. Cholera (5), " " " envelope and paper No growth. Cholera (6), " " " newspaper No growth. Plague (7), " " " towel No growth. FORMALDEHYDE AS A DISINFECTANT. 25 Plague (8), infected disc inside envelope and paper No growth. Plague (9), " " " newspaper No growth. Diphtheria (10), " " " towel No growth. Diphtheria (11), " " " envelope and paper No growth. Diphtheria (12), " " " newspaper Growth. Table No. 27. Character of test same as Table No. 1. Amount of alcohol used, one quart; time of exposure, six hours. Plague (1) No growth. Anthrax (3) No growth. Plague (2) No growth. Diphtheria (4) No growth. Cholera (5) Growth. Character of test: Infected discs inside the following packages. Amount of alcohol used, one quart; time of exposure, six hours. Plague (1), infected disc inside sheet of paper and envelope No growth. Plague (2), " " " towel No growth. Plague (3), " " " single newspaper Growth. Cholera (4), " " " sheet of paper and envelope No growth. Cholera (5), " " " towel... No growth. Cholera (6), " " " single newspaper No growth. Diphtheria (7), " " " sheet of paper and envelope No growth. Diphtheria (8), " " " towel No growth. Diphtheria (9), " " " single newspaper Growth. Anthrax (10), " " " -sheet of paper and envelope No growth. Anthrax (11), " " " towel No growth. Anthrax (12), " " " newspaper.... Growth. Table No. 28. Table No. 29. Character of test same as Table No. 1. Amount of alcohol used, one pint; time of exposure, six hours. Plague (1) No growth. Plague (2) Growth. Anthrax (3) No growth. Diphtheria (4) Tube broken. Cholera (5) No growth. Same test. Plague (1), infected discs inside sheet of paper and envelope No growth. Plague (2), " " " " " " " " No growth. Anthrax (3), " " " " " " " " Growth. Diphtheria (4), " " " " " " " " Growth. Cholera (5), " " " " " " " " No growth, 26 FORMALDEHYDE AS A DISINFECTANT. Table No. 30. Character of test same as Table No. 1. Amount of alcohol used, one pint; time of exposure, twelve hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. Same test. Plague (1), infected discs inside sheet of paper and envelope No growth. Plague (2), " " " " " " " " No growth. Anthrax (3), " " " " " " " " No growth. Cholera (4), " " " " " " " " No growth. Diphtheria (5), " " " " " " " " No growth. Table No. 31. Character of test same as Table No. 1. Amount of alcohol used, one pint; time of exposure, twelve hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) Growth. Diphtheria (4) No growth. Cholera (5) No growth. Table No. 32. Character of test same as Table No. 1. Amount of alcohol used, one and a half pints; exposure, twelve hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3). No growth. Diphtheria (4). No growth. Cholera (5) No growth. Character of test same as Table No. 1. Amount of alcohol used, a pint and a half; exposure, twelve hours. Table No. 33. Piagae (1) No growth Plague (2) No growth. Anthrax (3) ..... No growth. Diphtheria (4) No growth. Cholera (5) No growth. These experiments show that the oxidation of one pint of methyl alcohol in the lamp above described, FORMALDEHYDE AS A DISINFECTANT. 27 with an exposure of twelve hours, is hardly sufficient for superficial disinfection in a room of one thousand cubic feet of space, as it will be seen that a growth occurred in Table No. 31 (see Anthrax No. 3), where a pint of alcohol was used, with twelve hours' exposure. There- fore, a pint and a half should be used for each one thousand cubic feet of space, as indicated in Tables 32 and 33. Disinfection by the Heating of Paraformalde- hyde (Paraform) in the Form of Tablets or Pastilles. In a previous part of this article, in describing the use of formaldehyde solution (formalin), reference was made to a white soapy or chalky substance which is found after the formalin has been exposed for some time. This is now known to be paraformaldehyde, and is made into tablets for disinfection. Recently, Schering & Co., the manufacturers, have devised an apparatus for heating these tablets which is simple and easily manipulated. It consists of a small sheet-iron cylinder resting on a tripod, and supporting at the upper end an iron cup, the upper portion of which is connected with the edge of the cylinder by wire netting, thus allowing a draught from underneath, which facili- tates the removal of the gas from the cup. An alcohol lamp under the cylinder furnishes the necessary heat. The pastilles are placed in the cup, the lamp lighted, and the room closed. The following experiments with this method of se- curing formaldehyde for disinfection were made in a room of one thousand cubic feet of space: 28 FORMALDEHYDE AS A DISINFECTANT. Table No. 34. In this test an improvised apparatus was made by using a Bunsen burner under a small wire tripod, upon which was placed a shallow metal dish holding the pastilles. The Bunsen burner was operated by a gas meter outside of the apartment. At first the heat was too great, and once or twice the tablets were set on fire, and it was necessary to enter the room to extinguish the flame. The heat, however, was re- duced, and remained in this manner for three hours, at the end of which time the tablets were burned to ashes. The gas was then turned off. Character of test: Infected discs inside the following packages. Num- ber of pastilles used, forty ; time of exposure, twelve hours. Anthrax (1), infected disc inside of towel No growth. Anthrax (2), " " " " envelope and paper.... No growth. Anthrax (3), " newspaper Growth. Cholera (4), " " " " towel No growth. Cholera (5), " " " " envelope and paper... . No growth. Cholera (6), " " " " newspaper Growth. Plague (7), " " " " towel No growth. Plague (8), " " " " envelope and paper.... No growth. Plague (9), " " " " newspaper Growth. Diphtheria (10), " " " " towel No growth. Diphtheria (11), " " " " envelope and paper. ... No growth. Diphtheria (12), " " " " newspaper Growth. Table No. 35. lu the second test the apparatus devised for this special purpose was used, which is an improvement, inasmuch as the lamp is so con- structed that the heat can be properly regulated, and the alcohol con- tained is sufficient to keep the lamp burning for three or four hours, by which time the tablets are reduced to ashes. Character of test same as Table No. 1. Number of tablets used, forty; time of exposure, twelve hours. Plague (1) No growth. Plague (2) No growth. Anthrax (3) No growth. Diphtheria (4) No growth. Cholera (5) No growth. Since this article was prepared for publication, an apparatus for the production of formaldehyde which FORMALDEHYDE AS A DISINFECTANT. 29 possesses considerable merit lias been placed upon the market by the Sanitary Construction Company. It consists of a copper reservoir having a capacity of about three quarts. From the bottom of this leads a one- fourth-inch copper tube which two inches lower down forms a coil. The lower end of the coil is continuous with a brass tube of the same diameter, which ends about four inches above the reservoir in a rubber tube having a nozzle sufficiently small to be passed through a key- hole or any other small opening. Underneath the coil is placed a Swedish lamp, which furnishes the necessary heat. The formaldehyde solution (formalin) which is placed in the reservoir is allowed to slowly enter the coil by means of a valve. At this point it is acted upon by the flame of the lamp underneath, and as a result the gas contained is discharged through the small tube into the apartment to be disinfected. The advantages claimed for this instrument are as follows: That the formalde- hyde solution (formalin) can be used alone without the addition of a neutral salt, thereby dispensing with the pressure which is required when this mixture is used in an autoclave. As there is no need of the employ- ment of pressure in releasing the gas, the instrument can be made of light material and comparatively cheap. This apparatus will be favorably considered, inasmuch as the autoclave devised by Trillat, and also the method of combining chloride of calcium with the formalde- hyde solution for use under pressure in an autoclave, has been patented by a French company with which Trillat is now connected. Experiments which I have made with this apparatus would thus far show that the results are practically the same as those derived from the autoclave; it also has the advantage possessed by the 30 FORMALDEHYDE AS A DISINFECTANT. Trillat apparatus of rapidly releasing from outside the formaldehyde into the apartment to be disinfected. However, I should prefer to have further experience with this instrument before deciding as to its relative value. The Use of Ammonia to Neutralize Formaldehyde Gas.-It would appear from the prominence given this agent in connection with the use of formaldehyde that its function was misunderstood. The use of ammonia is not by any means a part of the disinfection with formaldehyde, and its employment is only indicated when the odor is objectionable and a desire is expressed to neutralize it. This may occur in a private residence, or, occasionally, where the apartment is needed for sleeping purposes. As a matter of fact, after the apart- ment which has been subjected to treatment is opened and well aired, or the clothing hung outside, the odor of the formaldehyde soon disappears. Besides, the use of ammonia presumably cuts short the disinfecting properties of the formaldehyde, whereas it should be continued as long as possible. If it is deemed advisable in any case to use ammonia, it should, if possible, be used in a compressed form. Ammonia can now be obtained in New York city in small cylinders contain- ing one pound. The cost is no greater than for the water of ammonia, and the contents of one of the cyl- inders will sufficiently neutralize the odor of formalde- hyde present in a room having a space of two or three thousand cubic feet. I have used ammonia in this form from a large cylinder for some time in the room used for experimental purposes in order to neutralize the formaldehyde preparatory to another test. Investigations as to the Effect of Formaldehyde upon FORMALDEHYDE AS A DISINFECTANT. 31 Insects, Animats, etc.-In conjunction with the experi- ments above cited I have carefully inquired into the effect of formaldehyde upon insects, fowls, guinea-pigs, mice, etc., by placing them in the apartment during disinfection under different circumstances and during various periods of time, ranging from three to fifteen hours, and in no instance has death ensued. Occasion- ally a guinea-pig would show evidence of an inflamma- tory condition of the respiratory tract; this, however, was uncommon. Importance of Testing the Preparations used for Dis- infection.-When it is considered how generally the for- maldehyde solution (formalin) is selected as the agent from which the gas is obtained for disinfection, the necessity of knowing the exact amount of formaldehyde which it contains is evident. All commercial products are liable to deterioration and adulteration. A lot of formaldehyde solution (formalin) may to-day contain thirty-five per cent, of formaldehyde gas and the next lot probably thirty per cent, or less. It may also contain a large amount of methyl alcohol, sufficient in some cases to constitute an element of danger. If a pint of formaldehyde solution, either alone, mixed with chloride of calcium, or in any other form, is regarded as sufficient for the disinfection of a room of a given space, it is es- sential that the percentage of formaldehyde should be known to constitute a standard upon which to work, and the subsequent supply of this agent should conform to the standard, or the difference should be noted. From the beginning of my experimental and practical work with this agent all the formaldehyde preparations used have been carefully tested to ascertain the amount of formaldehyde contained. This has been under the su- 32 FORMALDEHYDE AS A DISINFECTANT. pervision of Dr. Ernst J. Lederle, the consulting chemist of this department. In conjunction with this Dr. Lederle has very carefully investigated formaldehyde from a chemical standpoint, and the result of his work, which is of great value and interest, will be given in this issue of the New York Medical Journal. It is also essential that the methyl alcohol used in the disinfecting lamp should be tested. Conclusion.-A careful analysis of the results ob- tained in the experimental investigation to determine the value of formaldehyde as a disinfectant will show that this agent can not be depended upon for disin- fection where deep penetration is required. It can, however, be relied upon to penetrate letters and other thin packages if placed in an air-tight chamber, as in the apparatus referred to on the James W. Wadsworth. It is here that the importance and value of a vacuum is appreciated. Packages of the character just de- scribed are usually penetrated in a comparatively tight room. This has been proved not only by the germicidal effect upon the micro-organisms contained, but by the effect on blotting paper, ribbons, and silk, colored with fuchsine and magenta, and placed inside of letters, the envelope being tightly sealed. The change of color is very apparent upon opening the package after treat- ment. In packages made of blankets, clothing, etc., the action of formaldehyde upon infected discs placed in- side is uncertain and not always the same. As a rule, penetration does not occur; at least the organisms are not generally killed. This uncertainty would seem to decide the inefficiency of formaldehyde for deep pene- tration . For superficial disinfection-i. e., of hangings, furniture, clothing, furs, silks, and other articles which FORMALDEHYDE AS A DISINFECTANT. 33 can. be spread out and the surfaces exposed-formalde- hyde is an agent of undoubted value, particularly as it does not, as a rule, injure the finest fabrics, and there- fore may be safely used in an apartment furnished with delicate paper hangings and furniture. In the selection of the method for disinfection with formaldehyde, it is evident that the use of a formalde- hyde solution simply exposed on pans is not to be con- sidered, provided other methods are available. The heating of pastilles of paraformaldehyde is a simple, effective, and neat method of securing the gas, al- though at present it is a comparatively expensive one. It is necessary, however, that the apparatus for heating the pastilles should remain in the apartment until the time for disinfection has expired. The gas is there- fore evolved slowly, and its release depends upon the proper performance of a lamp which can not be kept under observation. For the same reason it may not burn sufficiently long to reduce the pastilles to ashes, or an accident may happen. I only refer to these as possibilities. The lamp for the generation of formaldehyde by the oxidation of methyl alcohol, which has already been described, is also an effective method, as the experi- ments above shown will prove. This method of secur- ing the gas is considerably cheaper than the preceding one-a pint and a half of wood or methyl alcohol, val- ued at twenty cents, being sufficient for the disinfection of a room having a space of one thousand cubic feet, whereas the expense of the pastille for this purpose is about seventy-five cents. Like the apparatus just de- scribed, the lamp can be purchased for a comparatively small sum, is easily manipulated, and is very satisfactory 34 FORMALDEHYDE AS A DISINFECTANT. for house disinfection. However, it is practically subject to the same criticism-i. e., that the process is com- paratively slow, and the lamp remains in the apartment, and not under observation, until the disinfection is completed. In a structure subject to change of posi- tion, as a ship, it is not improbable that an accident may occur. In the use of the autoclave and the new apparatus above referred to, we have a method by which the for- maldehyde is rapidly released and conveyed to the apart- ment to be treated, and when this is finished, the instru- ment, which is operated from the outside, can be removed. In this way the material to be treated is sub- jected to almost the entire volume of gas before any considerable leakage from the room may occur, whereas in the slower methods, if the room is not made tight, at no time is the material in the room acted on by all or nearly all the gas generated. Short exposures are there- fore only justified in cases where the gas is rapidly re- leased into the apartment by the autoclave or a similar apparatus. Further, this method does not require that the apparatus be left in the apartment; thus is avoided the possibility of a faulty action of the instrument or the chance of a change in its position. For general use, therefore, particularly for ship disinfection, I am in favor of this method of disinfection. The New York Medical Journal. A WEEKLY REVIEW OF MEDICINE. EDITED BY FRANK P. 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