CHEESE. 63 



In the above operation, great care must be taken to exhaust 

 thoroughly with ether ; the mass may be got out of the flask 

 and powdered up in a mortar if necessary. It is also well to 

 moisten -wdth a few drops of strong alcohol before adding the 

 ether. Having, as aforesaid, obtained from the cheese an 

 ethereal solution of the fat, and having disposed of this 

 ethereal solution, we return to the mass which refuses to dis- 

 solve in the ether. This consists of caseine, possibly of milk- 

 sugar as well, and certainly of salt and phohphate of lime. 

 It is to be treated first with strong alcohol, and then washed 

 with boiling water, and then dried in a platinum dish. The 

 dry residue (which consists of caseine and phosphate of limo 

 or ash) is then weighed, ignited, and weighed again : the 

 difference, i. e., the loss on ignition, is the caseine. 



In order to determine the milk-sugar, the alcoholic and 

 aqueous solutions are to be evaporated to dryness, the residue 

 weighed and ignited, and the loss on ignition will include 

 the sugar. 



In analysis of cheese it is necessary that a caution should 

 be given respecting the large amount of ash in cheese. 

 As much as 7 per cent, of ash may be present in cheese, 

 without adulteration with mineral matter having been 

 practised. 



It has been stated that oxide of lead has been found in 

 cheese. Should any such case arise, it is very easily dealt 

 with. The cheose-ash (which, in such a case, should be got 

 in a porcelain crucible, since lead attacks platinum) is tested 

 for lead by means of sulphuretted hydrogen. 



