84 PUBLIC HEALTH CHEMISTRY 



too low, and the mineral salts too high. Paget's Perfected 

 Milk Food is a concentrated humanized milk of this class. 



Dirt in Milk. In Dresden, a standard of not more than 

 8 mgr. per litre exists. In this country Dr. Houston has 

 suggested (1905) two standards for dirt in milk : 

 (1) Amount of filth that settles on standing to be less than 

 100 mgr. per litre ; (2) This apparent filth is diluted 

 with water and put in centrifuge, when amount of deposit 

 should be less than 50 mgr. per litre. Otherwise expressed, 

 (1) is 10 parts per 100,000, and (2) is 5 parts. 



CREAM : CONDENSED MILK : INFANTS' FOODS. 



Cream. The composition is similar to that of milk, 

 but the fat is much higher in amount. No standard is laid 

 down in this country ; but in the state of New Hampshire, 

 cream must contain 18 per cent of fat. Cream is at times 

 thickened by the addition of such agents as gelatin, starch 

 paste, saccharate of lime (called viscogen), and condensed 

 milk. 



Colouring with annatto and coal-tar d^^es is known. 

 Annatto may be detected by adding bicarbonate of sodium, 

 and then immersing a strip of white filter-paper and stand- 

 ing overnight. A brown stain indicates the presence of 

 annatto. Coal-tar dyes of the azo group give a pink colour 

 with diluted mineral acids. 



Fat is estimated by the Leffmann-Beam process : 

 2 grams, of cream are mixed with 12 c.c. of water, and the 

 mixture is poured into the bottle, the remainder of the 

 procedure being as before (page 75). The result is multi- 

 plied by 777. The Werner-Schmidt and Adams' processes 

 may also be used. 



The Departmental Committee on Preservatives advised 

 that only borax and boracic acid be allowed in cream, and 

 in an amount not exceeding 0-25 per cent, expressed as 

 boric acid ; and the amount to be notified by a label 

 affixed. 



Cream prepared by centrifugalizing methods contains 

 45 to 65 per cent of fat. Devonshire, Cornish, or clotted 

 cream is prepared by warming milk in pans for several 



