PJn/sical and Chemical Papers. 85 



salts, so it seems, and 1 am of the opinion that it throws some 

 light on the jellying principle of fruit jellies. For instance, 

 investigators have proved that fruit juices containing acid and 

 pectin can be made into a jelly by heating, then adding sugar 

 and heating again; likewise, fruit juices having considerable 

 pectin and but little acid fail to jell, but if acid is added the 

 substance forms a jelly. My theory is that when the acid is 

 added to the calcium pectate, the calcium forms the salt of the 

 added acid and frees the pectic acid; the pectic acid pectase 

 clots the mass, and on cooling forms the jelly. When the 

 fruit juice contains sufficient amount of acid in itself and no 

 added acid is necessary, the action of the calcium pectate is 

 with the fruit acid, etc. That pectin can be hydrolyzed by acids 

 present if boiled sufficiently long has been proven by Gold- 

 waite. 



The following table, prepared and worked out by the writer 

 on actual experiments in the laboratory, places the above- 

 mentioned materials in six groups : Group I, the iodine solu- 

 tion group ; Group II, the acid nitrate of mercury group ; Group 



III, the concentrated solution of sodium borate group; Group 



IV, the solution of sodium hydrate group; Group V, the solu- 

 tion of mercuric chloride group, and Group VI, the solution of 

 cuprammonia group. 



A careful study of this group method shows that a new 

 method for testing agar-agar has been discovered. This test 

 is based on Groups II, III and IV, and the characteristic reac- 

 tions for agar-agar depends on a new test for acacia in Group 

 II, which is: the test with one drop of acid nitrate of mercury 

 plus the unknown water solution yields a stringy gelatinous 

 precipitate, soluble in excess of the reagent. Since the next 

 group reagent, the concentrated solution of sodium borate, in 

 Group III, only precipitates agar-agar and acacia, it is simply 

 a test to prove whether one or both are present in the unknown 

 water-soluble mixture. Going to Group IV, the solution of 

 sodium hydrate group, this group reagent does not precipitate 

 agar-agar, and hence if no precipitate is obtained agar-agar 

 is absent, although if a white cloudy precipitate occurs the 

 unknown is acacia, and if a brownish-yellow color occurs on 

 heating the unknown is tragacanth. Acacia may be further 

 tested for with a .solution of soluble basic lead acetate, which 

 gives a white gelatinous precipitate; and again tested for by 



