192 Miscellaneous Intelligence. 



and less soluble acid. He mistook it for, and sold it as, oxalic acid. 

 In 1819, Jahn described it in his Dictionary of Chemistry, and 

 distinguished it from both tartaric and oxalic acid. In 1826, Gay 

 Lussac showed that it was not tartaric acid, though its equivalent 

 number was almost the same. Some time after, Walchner also ex- 

 perimented on this acid. 



The acid is supposed to be peculiar to the grape of the Upper 

 Rhine ; but is probably present in all grapes. It may be obtained 

 by exactly saturating tartar containing racemic acid, with carbonate 

 of soda, and crystallizing most of the double salt formed. The 

 tartrate separates first, the far more soluble racemate remaining 

 dissolved ; when it crystallizes, its forms are different to those of 

 the tartrate. The mother liquor is to be evaporated, precipitated 

 by a salt of lead or lime ; and the separated precipitate decomposed 

 by sulphuric acid. Racemic acid first precipitates in crystals from 

 the acid solution, and then tartaric acid. Racemic acid requires 5 

 parts of water for its solution ; tartaric acid only 2 parts. 



The equivalent number was deduced from the racemate of lead. 

 This compound is much more soluble in excess of acid than tartrate 

 of lead, and usually covers the sides of the glass with a thin crystal- 

 line crust. The precipitated salt does not contain water, but the 

 crystallized salt does. The results of analysis were exactly the 

 same, both for the atomic proportion and the ultimate composition, 

 as for tartaric acid, (for which see the preceding page ;) so that this 

 substance furnishes a new example of the extraordinary fact, that 

 bodies composed of the same number of simple atoms may, never- 

 theless, possess different properties. 



Racemic acid has a different crystalline form from tartaric acid, and 

 also effloresces by heat, which tartaric acid does not. Pulverised 

 racemic acid, exposed to dry air at 64 F., for twenty-four hours, 

 was then dried in a current of air at 212 F., and lost 10.63 per 

 cent, of water. This loss did not increase, and it was found neces- 

 sary to use oxide of lead as a base, and apply heat above 212, 

 before all the water was expelled. The loss ultimately amounted 

 to 21.35 per cent., or two proportions of water. Of these, one 

 may be disengaged by heat alone, and the other by heat and a base. 

 As tartaric acid also contains two proportions of water, the differ- 

 ence in the characters of the crystals is not due to that substance. 



With potash, an acid racemate may be formed equally insoluble 

 with cream of tartar, and containing, like it, an atom of water of 

 crystallization. The crystals appeared to differ in form from those 

 of cream of tartar. The racemate of potash and soda, if it exist at 

 all, does not resemble Rochelle salts : a confused mass only is left, 

 and it is uncertain whether it is a double salt or a mixture of salts. 

 A racemate of potash and antimony may be formed analogous to 

 tartar emetic, but its crystals differ, being sometimes rhomboids, 

 sometimes rhomboidal prisms. As two tartrates of potassa and 

 antimony can be formed, one crystallizable, the other not, so also 



