§ 137. BUTTEll. CHEESE. 267 



whey, to boiling, filter out the coagulated albumen on a 

 dried and weighed filter, wash it first with water, then 

 with alcohol, and finally with ether, dry it at 100° C, and 

 weigh it. 



To the filtrate add a solution of mercuric nitrate, with 

 care to avoid an excess of the reagent. Lacto-protein is 

 precipitated, together with mercuric oxide ; collect the 

 j)recipitate on a weighed filter, wash it once with water 

 containing V\^ of nitric acid, then with pure water as 

 long as the filtrate is colored by hydrosulphuric acid, then 

 with alcohol, and finally with ether; finally dry it at 100° 

 C, and weigh it. 60" 1^ of it is to be estimated as lacto- 

 protein. 



Determine milk sugar in one-fourth of the whey (§ 84). 



Evaporate the remaining fourth to dryness in a plati- 

 num dish, dry the residue at 100°, and weigh it, ignite it, 

 and weigh again. Subtract the ash, albumen, lacto-pro- 

 tein, and milk sugar, from the total amount of matter in 

 solution in the whey, and call the remainder undetermined 

 extractive matter. 



BUTTER. CHEESE. 



137. a. Water. — Dry 50 grms. of the finely divided 

 substance at 100° C. as long as it loses weight ; butter is 

 more easily dried if a weighed quantity of quartz sand 

 is mixed with it. 



1). Fat, — Extract this with ether in the usual manner 

 (§ 87), collecting the insoluble residue on a weighed filter. 



c. Casein, — Wash the residue, insoluble in ether, well 

 with water, evaporate the aqueous solution to dryness, 

 dissolve the residue again in water, and, if any of it is 

 insoluble, collect this on the same filter, and wash the 

 whole again; dry the contents of the filter at 100°, and 

 weigh, ignite, and weigh again, and call the difference 

 between the first and second weighings, casein. 



