290 Notices of the Labours of Continental Chemists. 



but hygroscopic water ; further, that the citric acid which 

 Crasso separated from the residuous acid heated until the 

 disappearance of white vapours, and which he found by ana- 

 lysis to be Ci + 3 Aq, must no longer be considered as citric 

 acid dried at 100° C, but is the usual crystallized citric acid 

 which has remained unchanged, 



Wackenroder likewise contradicts the assertions of Robi- 

 quet and Crasso respecting the insolubility of citric acid in 

 aether: he found that rectified aether, dry as well as moist, 

 dissolved abundantly the melted acid, that the solutions did 

 not become milky in closed vessels, and on evaporation gave 

 a syrup which but slightly reddened dried litmus, and which 

 on standing exposed to the atmosphere gradually passed into 

 the crystallized state. 



Before quitting this subject we may notice the observations 

 of Berzelius {Atsberettelse, No. xviii.) on the views of Liebig 

 and Dumas on the constitution of organic acids : he rejects 

 them entirely, and states that the citrate of soda w hen heated to 

 190° may be a compound of two atoms of citrate of soda, and 

 one atom of aconate of soda. In a remarkable paper " On 

 certain Questions of the Day in Organic Chemistry," pub- 

 lished in Poggendorff's Amialen, xlvii. p. 289, which is prin- 

 cipally directed against Liebig's article " On the Composition 

 of Organic Acids," Annulen der Pharmacie, xxvi. p. 113, 

 Berzelius observes with regard to citric acid, that he has 

 found that when the citrate of soda dried at 190° C. was dis- 

 solved in water and placed aside to crystallize, regular crystals 

 of citrate but no aconate of soda was produced. As citrate of 

 soda is insoluble in alcohol, but aconate somewhat soluble, 

 he tried to extract the latter from the metamorphosed citrate 

 by this means, but he obtained much less than the theory 

 required. Citrate of silver when just precipitated is white 

 and voluminous ; it has then the formula Aq C* H^ 0% but 

 by heating, or even by standing in the fluid, it becomes hea- 

 vier, granular and crystalline, and has a composition similar 

 to that of the metamorphosed soda salt. The metamorphosed 

 silver salt was treated with alcohol and a quantity of hydro- 

 chloric acid not sufficient to decompose the whole of it ; the 

 mixture was well shaken until there was no more hydro- 

 chloric acid in the alcohol. The alcoholic solution when 

 evaporated left a perfectly uncrystalline syrup, which, dis- 

 solved in water, let fall a trace of citrate of silver; out of the 

 water was obtained a colourless syrup, similar to the aconitic 

 acid, and which when saturated with carbonate of soda gives 

 citrate of soda and aconate, which may be extracted by alco- 



