4 QUATERCENTENARY STUDIES IN PATHOLOGY 



compose the commercial solutions of formaldehyde, known as 



formaline, formol, etc. 

 3. Trioxymethylene, formed by the union of three molecules of 



formaldehyde. It is a white powder, giving off a strong odour 



of the gas. It is but slightly soluble in alcohol and water. 

 Formaldehyde gas possesses about the same specific gravity 

 as air, which renders it only slightly diffusible, although more so 

 than sulphur dioxide, in consequence of which it penetrates more 

 readily to all portions and corners of a room. Formaldehyde 

 combines with nitrogenous organic matter to form new com- 

 pounds, A few drops of formaldehyde added to white of egg 

 will prevent its coagulating by heat, and it is from this faculty of 

 combining directly with albuminoids forming the protoplasm of the 

 micro-organisms that the gas is supposed to derive its powers as a 

 germicide. Formaldehyde also readily unites with the nitrogenous 

 products of decay, fermentation, and decomposition, forming new 

 chemical compounds, which are both odourless and sterile. The 

 commercial solutions known as formaline, formol, etc., are said to contain 

 40 per cent, of formaldehyde gas. They are not always up to this 

 standard, and being volatile, there is a certain loss if they are not 

 properly kept. In winter there is a decided deterioration owing to the 

 polymerization and precipitation of the insoluble trioxymethylene, the 

 gas probably existing in solution in one of its polymeric states. 

 Formaline is probably dissolved paraformaldehyde. This is one of the 

 reasons why the simple heating or evaporating of the solution does not 

 always result in driving off the gas, but sometimes results merely in 

 dissipating the water, leaving a residue of solid paraform. Trillat has 

 shown, however, that this polymerization is prevented if the solution is 

 heated under pressure. 



A.— GASEOUS DISINFECTION WITH FORMALDEHYDE. 



Temperature, as with disinfectants in general, is an important factor 

 in disinfecting with formaldehyde. Disinfection with this gas should not 

 be attempted if the temperature is under 10° C, as the gas tends to 

 condense to paraform at lower temperatures. In cold weather it is 



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