Cheese 65 



caramel was present. Fuller's earth varies in efficiency, and 

 each sample should be tested on known solutions. 



Preservatives. — The preservatives used in milk may be found 

 in limited amount in butter, but a mixture of boric acid and 

 borax is often added as a substitute for salt. 



Glucose is sometimes used as a preservative, especially in 

 butter intended for export to tropical countries. Crampton 

 found as much as 10 per cent, in a sample of highly colored 

 butter intended for exportation to Guadeloupe. For the de- 

 tection of glucose the phenylhydrazin test might be used. For 

 determination Crampton used the following method : 10 

 grams of the sample were washed with successive portions of 

 convenient bulk, the solution made up to 250 c.c, and an aliquot 

 portion determined, as given for lactose on page 27. The solu- 

 tion may also be clarified by alumina-cream or acid mercuric 

 nitrate and examined in the polarimeter. 



Geisler found paraffin in oleomargarin; he uses the specific 

 gravity of the rendered fat as a sorting test, making special 

 examination only of samples that show below 0.9018 at ^^. 

 Microscopic examination under polarized light will often 

 show amorphous masses of paraffin mixed with the crystals of 

 fat. To isolate the paraffin, Geisler saponifies 2.5 grams of the 

 fat with 20 c.c. of alcohol and i gram of potassium hydroxid, 

 and dilutes the liquid with an equal bulk of water. By altern- 

 ately heating and cooling the liquid much of the unsaponifiable 

 matter may be collected. Most fats contain unsaponifiable 

 matter, and hence the material must be identified as paraffin. 



CHEESE 

 Cheese is the curd of milk which has been separated from 

 it, pressed, and undergone some fermentation. The precipita- 

 tion is produced either by allowing the milk to become sour 



7 



