Gerhard? s Organic Chemistry. 175 







here loses but one equivalent of its oxygen, and it is the residue 

 Sb 2 O a = Sb 2 3 — O which replaces H 3 ; we may represent 



SbO by Sb — H, and the composition of the salt is then 



C 4 H 4 KSb°0 6 +Aq, while that of tartaric acid is C 4 H, 6 . 

 At a temperature of 212° F. the combined water is expelled and 

 at 428° F. the equivalent of oxygen which we have considered 



as existing in Sb unites with two equivalents of the hydrogen and 

 is evolved in the form of water ; the reduction of the oxyd is 

 now complete and a new salt results, which is C 4 H Q KSb0 6 , 

 or as according to the notation of M. Gerhardt, the equivalent of 



a a 



antimony replacing hydrogen is Sb^ =Sb , it is C 4 H 2 K Sb u 6 . 



The oxyd of uranium is analogous in constitution to that of an- 

 timony, and M. Peligot has obtained a double tartrate of antimony 



and uranium, which, dried at 212° contains C 4 (H 4 if Sb°) 6 ; 

 at 392°, a decomposition similar to that of tartar emetic takes 

 place, and the whole of the hydrogen is expelled in the form of 



a _ a 



water, the residue contains C 4 U Sb „ = C 4 U 3 Sb 3 O 6 . Arsen- 

 ious arid boracic acids form with cream of tartar double salts, 

 analogous to tartar emetic and undergoing a similar decomposition 

 by heat.— (Precis, Vol. I, pp. 498-502.) 



These singular compounds are so far removed in many of their 

 characters from ordinary saline compounds, that it is difficult to 

 ^y in what view we are to regard them. 



The use of symbols to denote the forms in which the metal 

 ^places the hydrogen is merely for the purpose of illustration. 

 1° regard these as really equivalent substitutions would be to 

 ^°pt a principle which would involve much perplexity and con- 

 fusion in other cases, and it is better to view them, as in truth, 

 substitutions by residue, in which the idea of metaleptic substitu- 

 tion is not necessarily implied. The metal in them is frequently 

 R o longer recognizable by the ordinary tests ; thus in tartar emetic 

 th -e antimony is not precipitable by alkahes, and the power of 

 jhe tartaric and many other polybasic vegetable acids to prevent 

 Jhe precipitation of iron and alumina by ammonia is well known. 

 1 he oxalate of chrome and potash is but partially decomposed 

 eith er by potash or salts of lime. It is worthy of notice that the 

 volatile acids, a portion of whose hydrogen is metaleptic or re- 

 P'aceable by chlorine, do not like the tartaric acid form compounds 



m Jjjich M a is substituted for the hydrogen. 



The number of equivalents of oxygen in an acid bears a cer- 



ain relation to its basicity. A monobasic acid may contain two, 



"fee, or four equivalents, a bibasic acid from four to eight, and a 



l " D asic acid six or seven ; two, four, and six being the minima 



