REPORT ON CHEMISTRY. 
.701 
in a retort at a temperature insufficient to decompose it, a yel¬ 
low transparent gummy-like mass remains, which gives, with 
lime and alumina, insoluble gummy-like compounds,—with 
potash and soda, similar but soluble salts. Partially saturated 
with potash, a precipitate falls, which, saturated with soda, gives 
Rochelle salt. In this state Braconnot considers the acid to 
be an isomeric modification of the common tartaric acid. Ber¬ 
zelius* has observed a similar change in the acid by heating, 
and considers it probable that it may be analogous to the change 
produced upon phosphoric acid by the same means. 
Pyrotartaric acid. —The pyrotartaric acid discovered by 
Rose, has been lately investigated and analysed by Dr. Grunerf. 
When tartaric acid is distilled in a retort, there pass over acetic 
acid, pyrotartaric acid, an empyreumatic oil, and an insoluble 
acid which crystallizes in the neck of the retort towards the 
close of the operation. The pyrotartaric acid, freed from these 
mixtures, is obtained in needles and four-sided prisms, which 
fuse at 212° F., losing eight per cent, of water, and which vo¬ 
latilize totally in white fumes at 221° F. They are soluble in 
alcohol, in aether, and in three times their weight of cold water. 
The acid, as was already known, forms soluble salts with all 
the alkaline and earthy bases. That of soda crystallizes in 
cubes. It forms, also, crystallizable double salts with potash 
and barytes, soda and barytes, and oxide of lead and ammonia. 
Its composition, according to Griiner, is 
4 carbon 
3 hydrogen 
4 oxygen 
By experiment. 
= 24*2441 
= 3*030 > 
= 32*326 
743*8 = atomic weight. 
Pyroracemic—Pyroparatartaric acid. —When the para- 
tartaric acid is distilled in a retort at a temperature sufficient 
to decompose it, there pass over, as in the distillation of the 
tartaric acid, an empyreumatic oil, acetic acid, an insoluble 
acid which crystallizes in prisms, and a liquid volatile acid 
differing in properties from the pyrotartaric acid of Rose. 
This acid is extremely volatile, distilling over at a temperature 
much below 212°, and gives crystallizable salts, with potash, 
soda, barytes, lead, and probably the other bases. Saturated 
in the cold with any of these bases, it speedily deposits crystals; 
but if the solutions be concentrated by evaporation, or heated 
for a short time to the temperature of about 100° F., they re¬ 
fuse to crystallize, and form only, when left to themselves, a 
* Arsberdttelse, t832, p. 208. 
f Tromsdorf, xxiv. p. 55. 
