Products of Citric Acid at high temjjeratiires. 285 



cyanuret of potassium cannot have the same composition as 

 that obtained from a sesquioxide'or persalt, and the ferrocya- 

 nuret ; the former must contain three atoms of protocyanuret 

 of iron and one atom of sesquicyanuret, while the common blue 

 contains two atoms of sesquicyanuret of iron. M. Voelckel 

 has analysed the former substance in Wohler's laboratory ; it 

 was prepared by adding ferrosesquicyanuret of potassium 

 to excess of protochloride of iron. It contained, iron 

 25*589, potassium 5"284', cyanogen 33'684'. Probable for- 

 mula, (Fe- Cy" + 3 K Cy=) + 4 (Fe'^ Cy^ + 3 Fe Cy"-.) [Aji- 

 nalen dcr Pharmacies xxxv.) 



Double Carbonate of Lead and Soda. 



During his experiments on the atomic weight of carbon, 



Berzelius discovered a double salt of carbonate of lead with 



carbonate of soda ; it is obtained by dropping a solution of 



nitrate of lead into an excess of solution of carbonate of soda, 



and boiling the mixture. Its formula is Na C + 4 Pb C. 

 {Arsberattelse, xix.) 



Acid Products of Citric Acid at high temperatiires. 

 The researches of I^assaigne, Baup, Dahlstroem, Berzelius 

 and Robiquet, had led us to suppose that three acids were 

 formed from the decomposition of citric acid at high tempe- 

 ratures, which is fully confirmed by a series of experiments 

 by G. L. Crasso, recently published in the Aiinalen der Phar- 

 macie (vol. xxxiv. p. 53). The first formed is the aconitic 

 acid of Dahlstroem and Berzelius (Baup's acide citridiqiie) 

 OH-0' + Ag ; then the itaconic acid (pyraconitic acid, 

 Lassaigne's pyrocitric acid, and Baup's acide citricique) 

 C^ H* ()' + Ag. ; and lastly, citraconic acid (pyrociti'ic acid 

 of Robiquet and Lassaigne, Baup's acide citribique), isomeric 

 with the preceding. The two last appear to be bibasic, the 

 first tribasic. No aconitic acid is formed previous to the 

 disengagement of aceton and carbonic oxide. The two other 

 acids are products of the aconitic acid. No distillation was 

 continued longer than ten minutes. The acid first melts 

 and gives off' pure water, upon which white vinous acid and 

 combustible vapours are disengaged, which evidently contain 

 aceton and carbonic oxide. If the operation be now inter- 

 rupted, the residue dissolved in water and brought to cry- 

 stallization, pure unaltered citric acid is obtained, of which 

 the analysis gave the formula for the citric acid dried at 100°, 

 viz. Ci-H"'0" + 3 H-O; and besides which, a small por- 

 tion of uncrystallizable mother-ley proportional to the quan- 

 tity of aceton and carbonic oxide evolved. When further 



