MILK 



341 



of the mixture, on a water-bath, nearly to the boiling-point, with occasional 

 stirring. If formaldehyde is present a violet color is produced, while a brown 

 color develops in the absence of formaldehyde. In case of doubt the mixture, 

 after having been heated nearly to the boiling-point for about one minute, 

 should be diluted with 50-75 c.c. of water, and the color of the diluted fluid 

 carefully noted, since the violet color if present will quickly disappear. For- 

 maldehyde may be detected by this test when present in the proportion i : 250,000. 



(b) Salicylic Acid and Salicylates.Remont's Method. 1 Acidify 20 c.c. of milk 

 with sulphuric acid, shake well to break up the curd, add 25 c.c. of ether, mix thor- 

 oughly, and allow the mixture to stand. By means of a pipette remove 5 c.c. of the 

 ethereal extract, evaporate it to dryness, boil the residue with 10 c.c. of 40 per cent 

 alcohol, and cool the alcoholic solution. Make the volume 10 c.c., filter through 

 a dry paper if necessary to remove fat, and to 5 c.c. of the filtrate, which represents 

 2 c.c. of milk, add 2 c.c. of a 2 per cent solution of ferric chloride. The production 

 of a purple or violet color indicates the presence of salicylic acid. 



This test may form the basis of a quantitative method by diluting the final 

 solution to 50 c.c. and comparing this with standard solutions of salicylic acid. 

 The colorimetric comparisons may be made in a Duboscq colorimeter. 



(c) Hydrogen Peroxide. Add 2-3 drops of a 2 percent aqueous solution of 

 para-phenylenediamine hydrochloride to 10-15 c.c. of milk. If hydrogen peroxide 

 is present a blue color will be produced immediately upon shaking the mixture or 

 after allowing it to stand for a few minutes. It is claimed that hydrogen peroxide 

 may be detected by this test when present in the proportion i : 40,000. 



(d) Boric Acid and Borates. To the ash, obtained according to the directions 

 given in Experiment 4, page 345, add 2 drops of dilute hydrochloric acid and i 

 c.c. of water. Place a strip of turmeric paper in the dish and after allowing it 

 to soak for about one minute remove it and allow it to dry in the air. The 

 presence of boric acid is indicated by the production of a deep red color which 

 changes to green or blue upon treatment with a dilute alkali. This test is sup- 

 posed to show boric acid when present in the proportion i : 8000. 



Quantitative Analysis of Milk 



1 . Collection of Human Milk for Analysis. There are two methods 

 of obtaining samples of breast milk for analysis. 2 



First Method. Express all the milk from one breast and mfc thoroughly. 

 Second Method. Draw one ounce of milk before nursing and one ounce after 

 nursing. Mix the two samples throughly. The best time for obtaining samples 

 is 9-10 o'clock in the morning. 



2. Specific Gravity. This may be determined conveniently by 

 means of a Soxhlet, Veith, or Quevenne lactometer. A lactometer 

 reading of 32 denotes a specific gravity of 1.032. The determina- 

 tion should be made at about 6oF. and the lactometer reading 

 corrected by adding or subtracting 0.1 for every degree F. above or 

 below that temperature. 



1 For other tests see Sherman's Organic Analysis, Second Edition, p: 378. 



2 Talbot: Jour. Am. Med. Ass'n, 73, 662, 1919. 



