Commissioner of Agriculture. 315 



REPORT OF JOHN A. MILLER. 



Hon. George J. Zillig, Esq., Assistant Commissioner of 

 Agriculture: 



Dear Sir. — Inasmuch as the compound known commercially 

 as " formalin " or " formal," is being used to some extent abroad 

 for the preservation of milk, I have deemed it advisable to look 

 into the subject of its use,, especially from the standpoint of its 

 detection and identification. Personallv I have not, thus far, 

 found any market samples of milk containing this preservative. 



What is Formalin? 



Formalin or formal, as supplied the trade, is a 40 per cent, 

 solution of formic aldehyde in water. The solution used in the 

 tests below enumerated^, contained 37 per cent, of formic aldehyde. 



Formic aldehyde is the product of tlie partial oxidation of 



methyl alcohol (wood alcohol). It is not 'necessary to follow the 



chemical reaction which takes place in the preparation of this 



compound, other than, that during the oxidation the methyl 



alcohol gives up two of its hydrogen atoms to the oxygen which 



is acting upon it. 



Method of Detection. 



The method which was finally adopted as giving the most 

 satisfactory results is as follows: 



Two hundred cubic centimeters of milk are mixed with 100 

 cubic centimeters of distilled water in an Erlenmeyer 

 flask, and 35 to 40 cubic centimeters distilled over. Care 

 and watching are necessary during the distillation, as the milk is 

 apt to froth a great deal. One-half of the distillate is put into 

 a perfectly clean test tube, and to this is added six drops of a 

 solution prepared by dissolving one dram of silver nitrate in 25 

 cubic centimetres of water to w'hich dilute ammonia has been 

 added until the precipitate formed is just redissolved, and adding 

 five to ten drops of ammonia in excess, and then make the solu- 

 tion up to 50 cubic centimeters. The tube, well stoppered, is set 

 aside in the dark, and examined from time to time. In from 

 two to twelve hours, a mirror or a black precipitate of silver will 

 have formed, if formic aldehyde is present. 



