342 
MANUFACTURE OF PARATARTARIC ACID. 
combinations, by Dr. Thomas Thomson. A striking difference be- 
tween tartaric and racemic acids is exhibited, when we drop solu- 
tions of these acids into solutions of chloride of calcium. The 
former occasions no precipitate, while the latter throws down a 
copious deposit. Thus we see that racemic is a more powerful 
acid than tartaric. Accordingly , it is capable of decomposing va- 
rious tartrates and taking the place of their acid. M. Kestner, 
a manufacturer of tartaric acid at Thann, a small town in the de- 
partment of the Vosges, first noticed the existence of this acid about 
the year 1817. A few months since he called the attention of M. 
Pelouse to the circumstance, that of late years he had not met 
with this acid in the ordinary course of maufacturing tartaric acid. 
It would appear from M. Kestner's letter toM. Pelouze, and which 
was read at one of the sittings of the Paris Academy of Sciences, 
that in the years 1822 to 1824, he was in the habit of decomposing 
the crude tartars he employed, by carbonate of lime, using a large 
excess of sulphuric acid in the decomposition of the tartrate of 
lime, and passing a current of chlorine gas through the tartaric 
acid solution for the purpose of removing its color; but that since 
1824, he has been accustomed to decompose the tartar by caustic 
lime, using a slight excess only of sulphuric acid in the decomposi- 
tion of the tartrate of lime, and omitting the bleaching process. 
During the period he employed the first named process, he fre- 
quently detected the presence of paratartaric acid, especially in 
winter ; but from the time of his discontinuing that process up to 
the present time, he has failed in obtaining the slightest indication 
of it. He furnishes no analysis of the tartars employed at those 
respective periods, and confesses himself quite at a loss to account 
for these phenomena. He concludes by expressing the hope, 
that the future researches of scientific men may throw some 
light upon the obscurity in which this subject is at present in- 
volved. 
Recent investigations have led to the conclusion that most tar- 
tars contain a certain portion of paratartaric acid, which is lost in 
the process at present employed in the manufacture of tartaric acid. 
This fact may serve to account for the deficient results sometimes 
obtained. 
