106 Dr. Thomas Thomson [Aug. 



II. RACEMATE OF POTASH. 



This salt is easily procured by saturating liquid racemic 

 acid with carbonate of potash, and concentrating the solu- 

 tion till it deposits crystals. 



The crystals of this salt are large transparent prisms. 

 The primary form seems to be a right oblique four-sided 

 prism. The faces of which are inclined to each other 

 nearly at angles of 120° and 60°. The edges 60° are usually 

 replaced by planes, which, however, are not tangent planes, 

 as they form unequal angles with the two adjacent faces of 

 the prism. Sometimes all the four edges are replaced, 

 making the prism eight-sided. The terminal edges are 

 always replaced by tangent planes, which frequently con- 

 ceal the terminal plane and convert the summit of the 

 crystal into a four-sided pyramid, with very unequal faces 

 in point of size. 



The taste of the salt is saline, harsh and bitter. Its 

 specific gravity is 2*08. It is not sensibly soluble in alcohol. 

 At the temperature of 55° 100 water dissolve 112*59 of the 

 crystallized salt. 



It has been shewn in a preceding part of this paper, that 

 the salt is a compound of 1 atom acid and 1 atom potash. 

 To determine the quantity of water, 87*5 grains of anhydrous 

 carbonate of potash were just saturated with crystals of 

 racemic acid. The solution being evaporated to dryness 

 in a gentle heat weighed 155*7 grains. Now, it contained 

 60 grains of potash and 82*5 of racemic acid. Hence, its 

 constituents were obviously 



1 atom racemic acid . . 8*25 

 1 atom potash .... 6*00 

 Water 1-32 



15-57 

 1*32 exceeds an atom of water by about ^th of an atom. 

 This small excess, doubtless, consisted of water lodged 

 mechanically among the particles of the salt. The chemi- 

 cally combined water in the salt is 1 atom or 1*125, and 

 the atomic weight of the crystals 15*375. 



When racemate of potash is heated, it melts and gives off 

 water. It then becomes brown, swells up and the acid is 

 decomposed. But it scarcely burns with flame unless when 



