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19. "New Fragments," Atoms, olecules, and Ether waves.
23. Frankel: "Text-Book of Bacteriology."
Babes: "Twentieth Century Practice, Supplement." Tetanus. 25. Roux and Borrell: "Annals Pasteur Institute," 1898, No. 11. 26. Babes: "Twentieth Century Practice, Medical Supplement."
27. Henry Hobart Hare:
"Philosophical Society," Philadelphia, Jan
uary 27, 1883.
28. Encyclopedia Britannica, 9th American Edition. Physiology.
A NEW FORMALDEHYDE GENERATOR.
S. M. MORRIS, M. D..
Some months ago when my attention was first attracted to the subject of disinfection by formaldehyde, I was struck while searching the literature of the subject with the practical unanimity of opinion among experimenters that formaldehyde was to be considered only a surface disinfectant and that it possessed very little power of penetration.
Since the density of formaldehyde gas is almost exactly that of air, being in the ration of 15 to 14.42, and since the rates of diffusion of gases are functions of their densities, theoretically there should be no reason why formaldehyde gas should not have the same power of penetration as air and be capable of going where air can go in the same period of time.
Before continuing the discussion of this phase of the subject I wish to mention very briefly the various methods of disinfection by formaldehyde which are in use at the present time, or rather the more important methods only. The most widely used method, perhaps, consists in heating the aqueous 40 per cent solution of the gas in water (formalin) either pure or containing glycerine or calcium chloride, and heating under pressure preferably, or more commonly in an open retort and carrying the vapors into the space to be disinfected by means of a tube thrust through a keyhole or other opening, the doors and windows having been previously closed and crevices stopped with cotton or by pasting strips of heavy manila paper over them. When the liquid is heated, which contains not only gaseous formaldehyde in solution, but also its polymerides, such as paraformaldehyde and trioxymethylene in an open retort, water is principally driven off at first in the form of steam and it is not until one-half or two-thirds of the liquid has been evaporated that the gas is evolved to any consider
able extent. It is recommended to use in this method from ten to sixteen ounces of formalin to each 1,000 cubic feet.
It has occurred to me that since this is the usual method of generating the gas that perhaps the method itself was responsible for the opinion that the gas had but little penetrating power. Since steam is driven off first, of course it condenses immediately upon the cool surfaces of the walls, fabrics, furniture, etc., in the apartment and when the gaseous formaldehyde follows later it simply redissolves in this film of moisture and goes no further than the water has gone, thus being superficial in action. In support of this view is the well known fact that the higher the temperature of the atmosphere the greater is the disinfecting or germicidal action of the gas, the increase in temperature decreasing the amount of condensation of the water vapor. This being the case the thought suggested itself to me to introduce the gas first with the minimum amount of water, allowing it to thoroughly diffuse and penetrate and then to introduce water vapor in considerable amount, later in amount sufficient to saturate if possible or to nearly saturate the atmosphere and thus fix as it were the gas in the tissues of the micro-organisms which have been reached by it. These advantage are possessed by my generator, to be afterwards described.
The second method of using formaldehyde consists in heating by means of a simple lamp, paraformaldehyde, which is a solid polymer of formaldehyde, which is by the heat converted into the gaseous form. By this method no water whatever is introduced into the atmosphere, other than that which it may happen to contain at the time, and therefore a larger amount of the agent is required than would be the case if moisture were added. By calculation I find that it requires about 758 grams of paraformaldehyde, or nearly 1.7 pounds, to each 1,000 cubic feet to produce two per cent by volume.
The third method is the one I prefer, because of its many advaninges and consists essentially in oxidizing the vapors of wood alcohol by passing them mixed with air over some oxidizing material.
Various lamps operating upon this principle have from time to time been constructed, but have not been generally used, the reasen being, in my opinion, because of the slowness with which they evolve the gas, for unless the gas is generated in large volume at once it leaks out of an ordinary apartment about as rapidly as it is generated. A small volume of formaldehyde acting for a long period of time is not nearly so efficacious as a large volume acting for a comparatively short period of time.
So far as I can learn all of these lamps have used as the oxidizing material asbestos cardboard impregnated with finely divided platinum. A lamp operating upon this principle can be easily constructed by any one by using an empty tin can or other suitable small vessel, cutting out a piece of asbestos cardboard to fit the top of the can, punching a number of small holes in the cardboard, soaking the cardboard in a solution of platinum chloride and then igniting it. This decomposes the platinum chloride, driving off the chlorine and leaving the platinum in a finely divided state on the cardboard. Next fill the vessel nearly full of wood alcohol, ignite the alcohol and hold the cardboard a few inches above the flame and after a minute or so lower the cardboard and be sure that the flame is extinguished. Immediately formaldehyde begins to be evolved, due to the vapor of the heated alcohol passing over the heated platinized asbestos and there undergoing oxidation into formaldehyde at the expense of the oxygen of the air. The chemical action keeps the platinum hot and the process will continue until the level of the alcohol in the vessel gets so low as to lessen the rate of evaporation to such an extent as to allow the platinum to cool, when the operation ceases. Very often the heat of oxidation is so great as to ignite the alcohol and it was invariably my experience while experimenting with this type of apparatus that every attempt to construct a device on a large enough scale to generate formaldehyde enough to be of practical service was attended with spontaneous ignition of the alcohol. Various other oxidizing materials were tried with the result that I found that asbestos wool impregnated with certain copper salts and then
ignited produced under proper conditions a very energetic evolution of formaldehyde gas and by enclosing such material between sheets of wire gauze I was enabled to bring it within an inch of the surface of the alcohol while in operation, without danger of igniting the alcohol, thus enabling me to use the heat of oxidation to the greatest advantage in increasing the rate of evaporation of the alcohol and therefore increase the rate of production of the formaldehyde. This latter point is of vital importance because one quart of alcohol oxidized within an hour in a space of 1,000 cubic feet is of greater value than a gallon oxidized within a period of several hours unless the room is absolutely tight so that none of the gas can escape, conditions, however, which are never even approximated in actual practice.
My device may be essentially described as follows: A bowl or basin packed with asbestos or other noncombustible absorbent material, into which wood alcohol is poured. Near the rim of the basin is a number of small holes, which can be closed by a movable band and which are intended to introduce air for the oxidation of the wood alcohol. Above the bowl is the oxidizing disk, consisting of the oxidizing material enclosed between sheets of wire gauze. Above this is a pan designed to contain water and above it a vessel to be afterwards described. To operate the generator the disk is raised by the small chains on the side for that purpose, anchored in the elevated position by attaching the ends of the chains to the small knobs, a mixture of wood alcohol and carbolic acid to the amount of 1,000 c. c. to the 1,000 cubic feet to be disinfected is poured into the basin by means of a flat shaped funnel, the holes in the rim closed, and the alcohol ignited. It is allowed to burn for a couple of minutes in order to get the disk hot, when the disk is lowered. Its edges dipping into a trough around the sides of the basin extinguish the flame. The holes are again opened and the pan having been previously filled with water, the operator leaves the room, which he usually is compelled to do immediately, owing to the energetic evolution of the gas. The room having been previously properly closed the door is closed and the device is left to itself for a period of from three to six hours.