COMMERCIAL MILK-.SUCAR. 



387 



above figures. Cane-sugar can be detected by treating a solution 

 with a little yeast and keeping at 55° C. for five bours ; milk- 

 BUgar shows no change in specific rotatory power, while the 

 presence of even 1 per cent, of cane-sugar will produce a marked 

 alteration. 



Dextrose is detected by an increase in the birotation ratio, 

 by the solubility, and by a decrease in the fall of temperature. 



Maltose and dextrin (present in commercial starch-sugar) are 

 detected by a lowering of the birotation ratio, a great increase 

 in the apparent percentage of milk-sugar, and in the solubility. 



Mineral adulterants will be easily detected by the high per- 

 centage of ash. 



The following are typical analyses : — 



Junkets. — This preparation is made by adding cane-sugar to 

 milk and curdling by rennet at a low temperature. It is a 

 sweetish gelatinous substance, and is usually eaten with nutmeg 

 and cream. 



Casein. — ^lany preparations of this protein are now on the 

 market, and, besides being largely consumed as foods, they are 

 employed in the arts for such purposes as sizing paper, as a 

 mordant, and for clarifying wines. 



Casein is prepared by precipitating the protein from separated 

 milk by means of an acid ; sulphuric or hydrochloric acids are 

 generally employed, but sometimes acetic acid or the lactic acid 

 of strongly acid whey is used. If a moderately pure protein 

 is desired the precipitated protein is dissolved in a small quantity 

 of alkali, and reprecipitatcd, but many of the preparations on 



