(259) Iodine Trichloride, ICl.. Iodine trichloride is in the form of orange-yellow needles. It is formed by heating iodine pentoxide (iodic anhydride) in hydric chloride. The iodine pentoxide liquefies, and is converted into iodine trichloride according to the following equation: I2O +10 HCl = 2 ICl2 + 5 H2O + 2 Cl2. The crystals are soluble in water; the solution has no action on starch. Iodine trichloride will probably be an important disinfectant, its power having been carefully determined by Dr. Otto Reidel. The following is an abstract of his research1:— Threads infected with anthrax spores were steeped in 1 per cent. and 1 per 1,000 solutions of ICl, for 24 and 48 hours. In all these cases there was complete disinfection, as proved by cultivation and also experiments on animals. Hay bacillus spores, experimented with in the same way, but using a 1 per cent. solution, were not disinfected in 8 hours, in 12 hours were imperfectly disinfected, in 24 were completely disinfected. Garden earth spores were disinfected in 19 hours with the same solution. Anthrax threads, containing no spores (because derived from the blood of an animal dying from anthrax), were completely disinfected in 2 hours by a 1 per cent. solution, and it was shown by experiment that this strength in activity was about equal to a 3 per cent. solution of phenol. A similar result was obtained in experiments with the Staphylococcus aureus, and the Staphylococcus derived from osteo-myelitis, a 3 per cent. solution of phenol and a 1 per cent. solution of ICl, acted effectually in equal times, the former, S. aureus, being killed in 14 minutes, the S. osteo-myelitis in 60 minutes. The cholera comma bacillus was killed in 1 minute by 5 per cent. solution ICl,; in 3 minutes by phenol of the same strength. Experiments were also made on the effect of small quantities of ICl, added to the nutrient material serving as a soil for the cultivations. It was found that so little as 1:3,000 prevented the growth of a variety of pathogenic 1 Arbeit aus dem Kaiserlichen Gesundheitsamte, 2 Band, 1887. organisms, such as the micrococcus from erysipelas, the streptococcus pyogenes, the anthrax bacillus, and the cholera bacillus ; but others required the proportion of ICl, to be in the nutrient gelatin as 1:850, and the bacillus derived from typhoid excreta resisted in even 1:500. This latter property of the typhoid bacillus has been utilized by Chantemesse and Widal to raise it from typhoid excreta (Gaz. Hebd. de Med. et de Chir., 1887, No. 9, 146). A practical test of its use to the surgeon was made by placing the hands in a putrid liquid, washing them in the ordinary way, then rinsing with a 1 per cent. solution of ICl, getting rid of the disinfectant by washing it off with sterilized water, finally submitting scrapings of the skin of the hands to cultivation; no growth followed. Lastly, the author compares the poisonous properties of IC, weight for weight with HgCl2 (corrosive sublimate) and phenol. These experiments were all made on rabbits, the poisons being administered by peritoneal and subcutaneous injection. ICl, in 1 per cent. solution, injected into a rabbit in the proportion of 45 grm. per 10 grms. of rabbit, had neither local nor general effect, but the same relative quantity in 10 per cent. solution caused local necrosis. The animals mostly lived; one died after 10 days. Other experiments showed that a fatal dose for a rabbit was somewhere near 9 grms.; while a subcutaneous injection of a 1 per cent. solution of corrosive sublimate killed 15 per 10 grms. of rabbit, and in a greater dilution of 1 per 1000. 32 per 10 grms. killed. Phenol was fatal when injected subcutaneously in the proportion of 348 per 10 grms. of rabbit. (260) Phenol. Carbolic Acid. Phenol. CHHO. When pure and absolute, phenol is in the form of white crystals; the crystals melt at 42:2° (108° F.). Boiling point, without decomposition, = 182° C. Water gradually added to phenol, so long as it dissolves, gives a liquid hydrate of the composition CH ̧O2H2O, equal to 27.7 per cent. of water. The solubility of the crystals in water is very nearly that of 1 in 11; a saturated solution in water will contain about 86 per cent. of phenol. It is far more soluble in weak alkaline solutions than in water. It is (when absolute) soluble in all proportions in alcohol, ether, benzine, carbon disulphide, and chloroform. (261) Cresol. Cresylic Acid, CH2HO. Cresol is known in three forms-meta-, para-, and ortho-cresol. Para- and ortho-cresol are respectively obtained by fusing the pure potassic salts of the two isomeric sulphonic acids produced on heating toluene with sulphuric acid with potassic hydrate. The three modifications are not in ordinary commerce. Specimens the author obtained from Kählbaum had the following general appearance and properties:-Meta- and para-cresol were both liquid, of a reddish colour: para-cresol had a most unpleasant odour; metacresol had the smell of ordinary cresol; ortho-cresol was in the form of needle-like crystals, odour pleasant and aromatic. The commercial cresol, which makes up the bulk of the cheaper fluid so-called carbolic acid, is of a red colour, and contains meta- and para-cresol, with perhaps some small quantity of orthocresol; the boiling point varies from 198° to 200° C. It is less soluble than phenol; a saturated aqueous solution will contain about 33 per cent. It is soluble in weak alkaline liquids, but is precipitated with excess of alkali. (262) Estimation of Impurities in Commercial Carbolic Acid. The chief impurities of the dark liquid carbolic acid of commerce are tar oils; their presence is ascertained, and their quantity approximatively estimated, by shaking a measured volume of the acid with twice its volume of pure soda solution of 9 per cent. strength. The cresylic and carbolic acids are dissolved by the alkaline liquid, while the oils separate—“ heavy oils" sinking to the bottom, "light oils" rising to the top; the volume in either case can be read off. These tar oils have not been shown to possess any disinfectant properties. If it is required to ascertain the relative mixtures of cresylic and carbolic acids, this is best done by a fractional distillation, collecting the various products and carefully measuring them. A process for this purpose has been given by Mr. Lowe, and has been quoted by Allen; the process is as follows: 100 c.c. of the sample are placed in a retort and distilled into a graduated vessel. The first 10 c.c. of the distillate contains water and oil; the volume of each is determined, and the receiver changed. The next portion should consist of anhydrous acid, and when the distillate amounts to 625 c.c., the receiver is removed and the distillation stopped. The residue in the retort consists wholly of cresylic acid and the higher homologues of cresylic acid. To ascertain the relative proportions of cresol to phenol in the 625 c.c., it is necessary to carefully ascertain the solidifying point which should be between 15.5° and 24° C., then imitation mixtures. of phenol and cresol are made until a known mixture is obtained with the same solidifying point, or of course the reverse process may be used, i.e., the liquefying point determined. (263) Carbolic Acid Powders are Powders which should contain Free Tar Acids. All carbolic acid powders that have for their basis lime, and are hence mixtures of carbolate and cresylate of lime, are absolutely useless, exerting no appreciable disinfecting properties. A good carbolic acid powder is that which is merely a mechanical mixture of the acid and the powder, as for example "Calvert's carbolic acid powder," which is made by adding carbolic acid to the siliceous residue resulting from the manufacture of aluminium sulphate from shale. Macdougall's disinfecting powder is also to be mentioned with approval; it is made by adding a certain proportion of crude carbolic acid to an impure sulphite of calcium prepared from the action of sulphur dioxide on ignited limestone. Carbolic Acid Soaps are soaps containing more or less free carbolic acid; it is doubtful whether they are of the slightest use for disinfecting purposes or are at all superior to ordinary soap. Trustworthy and impartial experiments of a strictly comparative character have however not yet been made as to this. (264) The Author's Experiments on the Disinfecting Powers of Phenol and Cresol. The author has made many experiments on the relative disinfectant powers of pure phenol, and the purest commercial samples of cresol obtainable (this is as stated a mixture of ortho-, para-, and meta-cresol) and with pure samples obtained from Kählbaum of ortho-, meta-, and para-cresol. Some of these experiments have been already published, others appear here for the first time. EXPERIMENTS ON THE DISINFECTION OF THE BACTERIUM TERMO. Phenol and Cresol.-These experiments were made by the "drop" method. Weighed quantities of pure crystalline phenol and of pure liquid cresol were dissolved in 20 per cent. alcohol in such proportion that the strength was exactly 1 per cent. Water which had been infected with the bacterium was measured from a burette into test-tubes, and definite quantities of the phenol or cresol solutions added; the volume of the whole being kept at 10 c.c., e.g., 3 c.c. of phenol solution, and 7 c.c. of the infected water would equal 0.3 per cent., 1 c.c. of phenol solution and 9 of the infected water would equal 0-1 per cent., and so on. At the end of twenty-four hours nutrient gelatin was infected by means of dipping a clean recently ignited platinum wire in the liquid, and then inserting the wire for a second or two in the gelatin, which had been previously liquefied. The following short table summarizes these experiments; the sign denotes no growth, the + sign denotes the first appearance of evident growth and liquefaction. |