Ixxxii GENERAL SUMMARY OF SCIENTIFIC AND 



and treating this with bromine gives tetrabromfluorescein, of which 

 eosin is the potassium salt. The price of eosin is 100 francs a kilo- 

 gramme. 



Weselsky has shown that jDhloroglucin is a very delicate test for 

 nitrous acid. Very dihite solutions of phloroglucin and toluidine 

 (or aniline) nitrate become dark orange on the addition of a few 

 drops of a dilute solution of potassium nitrite, and a cinnabar red 

 powder is thrown down. 



Jacquemin has examined the methods proposed for the detec- 

 tion of fuchsin in wine, founded on its tinctorial power. As is well 

 known, this substance is extensively used for this j)urpose. Pyroxy- 

 lin and wool may be dyed directly in the wine, but to prove the 

 presence of fuchsin finally, the ammonia process is necessary. 



Liebermann and Fischer have further examined chrysophanic acid, 

 the active principle of rhubarb. They find it to stand to emodin, 

 its associate, precisely as alizarin stands to f)urpurin, only both the 

 former are homologous with the latter, being derivatives of methyl- 

 anthracene, Chrysophanic acid is dioxymethylanthraquiuone. 



Graebe and Caro have made an extended investigation of rosolic 

 acid, restricting this name to tlie substance obtained by the action 

 of nitrous acid on rosaniline and subsequent treatment with w^ater. 

 They find that it is capable of giving a series of tetra-substitution 

 products, and is analogous, therefore, with the phthaleins of resorcin 

 and orcin described by Baeyer. Reduction yields both hydrorosolic 

 acid and leucorosolic acid, and from these come tetrabromleucorosol- 

 ic acid and hydrocyantetrabromrosolic acid. 



Hlasiwetz and Habermann have examined the chemical characters 

 of gentisin and of gentisinic acid, into which and phloroglucin the 

 former is decomposed. This acid by heat yields carbon dioxide and 

 hydroquinone. 



Butlerow has made some experiments with the milky juice of 

 CynancJium acutum, Linn. He finds in it a volatile alkaloid and a 

 white gum-resin, probably a phenol, to which he gives the name 

 cynanchol. 



Williamson has described some metallic derivatives of coumarin, 

 containing the metals sodium, potassium, barium, silver, and lead. 



Wartha has investigated more minutely the coloring matter of 

 litmus, and has shown that the commercial article always contains 

 indigo. He gives directions for preparing the coloring matter pure. 



Tiemann and Haarmann have described a method for the accu- 

 rate determination of vanillin in vanilla, and have shown that the 

 price of the commercial varieties is not always in accord with their 

 content in vanillin. 



Latour and Cazeneuve have separated from mahogany an astrin- 

 gent substance containing carbon, oxygen, and hydrogen, which is 

 crystalline, and identical with catcchin. 



