190 XORMAL MILK : ITS ADULTERATIONS, ETC. 



welded. The correction to be applied is small. For keeping 

 samples for a short period, say ten days, this method is good. 



Ether. — This preservative is nearly as good as chloroform ; 

 it is, however, not quite so good a preservative and is more 

 volatile. 



Collins recommends a mixture of ether and chloroform of 

 ■specific gravity 1"032, as it does not afiect the specific gravity 

 of the milk. The author has, however, shown that ether and 

 chloroform keep the fat in a liquid condition, and that the specific 

 gravity is lowered by this cause. The estimation of the fat 

 by the Gerber method is too high in the presence of chloroform. 



Terpenes, Thymol, Dichlorophenol, and Salicylic Acid. — 

 These keep the milk, but allow the cream to rise to the surface, 

 where it sets in a firm layer and is not easily redistributed. 



Hydrofluoric Acid and Fluoboric Acid. — The author has 

 proved that these substances, when added to fresh samples in 

 the proportion of | c.c. to 100 c.c. of milk, keep them in good 

 condition, and, after a year, analysis gives the same figures as 

 those previously found. They curdle the milk, however, so that 

 the sample must be well shaken to bring the precipitated casein 

 into a fine state of division ; a little of the bottle is dissolved 

 and the ash is thereby slightly increased. The author has found 

 this method to be one of the best. 



rormalin.— The addition of formalin has many advantages. 

 A. very minute amount of the 40 per cent, solution need be 

 added (2 drops per 100 c.c), and no correction is necessary for 

 30 small a quantity. 



Siegfeld finds that the presence of much formaldehyde in milk 

 has a tendency to increase the amount of fat by the Gerber 

 method. This may be obviated by adding 1 c.c. of hydrogen 

 peroxide, or better, 0"5 of a 40 per cent, solution of hydroxyl- 

 ^mine hydrochloride per 100 c.c. of milk, and correcting for 

 increase of volume. 



The formaldehyde, however, combines with the protein, and 

 •raises the apparent percentage of total solids and solids not 

 -fat. Bevan has also suggested that the milk-sugar is hydrolysed 

 into dextrose and galactose, as he found the increase in total 

 solids more than the total amount of formaldehyde added ; but 

 this has been disproved by Hoft. 



Potassium Bichromate, Mercuric Chloride, and Solid 

 Antiseptics. — These add considerably to the weight of the 

 total solids and solids not fat, and cannot, therefore, be recom- 

 mended. If fat only is to be determined they are efficient. 

 Siegfeld does not consider that the analysis of samples preserved 

 ■by potassium bichromate is trustworthy. 



Sterilisation may be resorted to. Certain changes take place. 



