274 SCIENCE AND PRACTICE OF DAIRYING. 



factor 6 -39, on the assumption that the albuminoid matter of the milk 

 contains 15 '65 per cent of nitrogen. 



(3) Determination of Ash. This may be carried out in a special sample 

 of the cheese, or on the portion which has been used for the determination 

 of water, observing the precautions which are necessary in this process. 

 The ash is determined by burning a small portion. 



(4) The Determination of Milk-sugar. The percentage of milk-sugar may 

 be determined in perfectly fresh cheese by difference, if all the remain- 

 ing determinations have been carried out in duplicate with great care. 

 If it be desired to determine the milk-sugar directly, this may be done in 

 a water extract, obtained by taking a portion of the cheese dried under 

 the air-pump, rubbing it up thoroughly with pure sea-sand, and boiling 

 it repeatedly with pure water. In order to separate the albumin from 

 this water extract before treating it with the copper solution, it is necessary 

 to acidify it with acetic acid, boil, and then filter. 



In a perfectly exact analysis of fresh cheese, it must be assumed that 

 the fat of the milk contains lecithin, and that, therefore, small quantities of 

 nitrogen will be found in the fat of the cheese. 



In the investigation of ripe cheeses there is no method which can be 

 recommended as suitable or trustworthy. Manetti and Musso recommend 

 the following: Determination of the percentage of water and bodies 

 volatile at 115 C. ; preparation of a carbon bisulphide extract; prepara- 

 tion of an alcoholic extract; preparation of a watery extract; determination 

 of the quantity of bodies insoluble in bisulphide of carbon, alcohol, and 

 water; determination of the ash; determination of ammonia; determina- 

 tion of the sum of the acids present; determination of the nitrogen; and 

 finally, the determination of the nitrogen and ash in the different extracts, 

 as well as the determination of the nitrogen and ash in the residues of the 

 different extracts. 



As an example of the chemical composition of certain kinds of fresh 

 cheese, and of products resembling cheese, the following figures may be 

 given : 



100-0 100-0 100-0 100-0 100-0 100-0 



