8o 



but it should not pass under a false name ; hence some 

 simple means for detecting it is desirable. 



Dissolve i gm. of sulphur in 100 c.c. of carbon disulphide 

 and an equal volume of amyl alcohol. This solution is 

 known technically as Halphen's reagent. In order to test 

 for cottonseed oil, mix equal quantities of Halphen's solu- 

 tion and the oil under consideration in a test tube. Immerse 

 this tube in a water bath as in Figure 26, and allow the 

 contents to heat for about twenty minutes. If a faint red 

 color appears, a small quantity of cottonseed oil is present ; 

 if a deep red color appears, a large quantity of cottonseed 

 oil is present. If there is no evidence of red, the oil ex- 

 amined does not contain cottonseed oil. 



EXPERIMENT 78. CHEMICALS AS PRESERVATIVES 



Mix the white of an egg with about ten times its weight 

 of water and put approximately equal portions of the mix- 

 ture into 6 test tubes. 



(a) To one of these test tubes add about 5 drops of car- 

 bolic acid solution ; to another, 2 gm. of borax ; to another, 

 2 drops of formalin ; to another, 2 drops of corrosive sub- 

 limate ; to another, a pinch of salt ; and to another, a pinch 

 of sugar. 



Shake the various test tubes thoroughly in order to mix 

 their contents, plug them with raw cotton, and set them 

 aside in a warm place. Note from day to day the appear- 

 ance of the different tubes, and state which chemicals 

 seem to be the best preservatives. Which of the preserva- 

 tives do you consider safe ? Illustrate the use of these in 

 preserving foods. 



