376 OTHER MILK PEODUCTS. 



of the methods of cheese analysis, of which the following is an 

 abstract : — 



Ash. and Mineral Matter. — From 10 to 15 grammes of the 

 cheese are burnt (preferably in a muffle) in a platinum basin. 

 The weighed ash is dissolved in 250 c.o. of water and an aliquot 

 portion used for the determination of chlorine (calculated to 

 sodium chloride). The portion insoluble in water may also be 

 dissolved in dilute hydrochloric acid and made up to 250 c.c. ; 

 in a mixture of equal aliquot portions of each of these solutions 

 the calcium and phosphoric acid may be determined. 



Water. — A weighed quantity of the cheese is mixed with 

 washed, ignited, and sifted quartz sand. For most cheeses the 

 proportion of 100 grammes to 400 grammes of sand is satis- 

 factory, but with very rich cheeses 500 grammes of sand are 

 taken. This sand mixture is used in all the estimations. For 

 the determination of the water, an amount of the mixture corre- 

 sponding to about 3 grammes of cheese is dried to constant 

 weight in the water-oven. 



Fat. — The dry residue from the water-determination is 

 extracted for twenty-four hours with water-free ether, which 

 has been dried over sodium. 



Witrogen — I. Total Nitrogen. — Ten grammes of the sand 

 mixture are analysed by Kjeldahl's method (p. 124). 



II. Applicability of Copper Hydrate to the Precipitation 

 of Albuminoids. — Formerly, Stutzer employed copper hydrate 

 to separate proteins and their primary cleavage products from 

 secondary products (amino-compounds, etc.). He has since found 

 that it only partially precipitates trypto-peptones (pancreas- 

 peptone), and, extending his experiments to cheese, finds that 

 there is sometimes a peptone present which is not completely 

 precipitated. 



III. Phospho-tungstic Acid as a Precipitant. — The con- 

 clusions of Bondzynski that phospho-tungstic acid is a suitable 

 separating agent are confirmed. By its means the proteins and 

 their primary cleavage products (albumoses and peptones) are 

 separated from the secondard products (phenyl-amino-propionic 

 acid, leucine, tyrosine, and other amino-compounds) and am- 

 moniacal compounds, all of which Stutzer classes as worthless. 

 The substances belonging to the first group may be further 

 divided into — (a) Indigestible nitrogenous matters ; (6) Albu- 

 moses and peptones soluble in boiling water ; and (c) Proteins 

 insoluble in boiling water. 



IV. Nitrogen in the Form of Ammoniaeal Salts. — An 

 amount of the sand mixture corresponding to 5 grammes of 

 cheese is mixed with 200 c.c. of water and the ammonia dis- 

 tilled, after the addition of barium carbonate. Magnesia and 



