126 Chemistry and Chemical Arts. 
solution of per-sulphate of iron, a deep bluish black precipitate, much 
less soluble than the tannate, and which being heated to ebullition 
in water, is decomposed with disengagement of carbonic acid. Dri- 
ed at 120° C., it is composed of, 
Carbo Mer Pens iO -A9S9 7 atoms or equivalents, 
Hydrogen, . . . 0.0349 GENE a 
Oxygen . . . . 0.4662 pense 6 
When gallic acid is heated in a retort to the temperature of 200° 
to 215°C.., itis changed entirely into carbonic acid gas, and into pyro- 
gallic acid, which condenses in crystalline plates of a shining white- 
ness, and whose composition is expressed by the formula C® H® O%. 
But if the temperature is suddenly raised to 240°, carbonic acid 
and water are disengaged, and there remains a black matter similar 
to charcoal, but which is a new acid, the metagallic, and whose com- 
position is expressed by the formula C* H* O?. 
Tannin under the same circumstances yields similar results: only 
at the temperature of 215° C., there is always produced a certain 
quantity of metagallic acid along with the pyrogallie acid. 
Pyrogallic acid possesses a whiteness like that of snow. It is ex- 
ceedingly soluble in water, alcohol and ether. It enters into fusion 
at 115° C., and into ebullition at 210°. At 250° it blackens, disen- 
gages water, and is converted into metagallic acid; it instantly re- 
duces the persulphate to the state of protosulphate, even in the cold 
without the disengagement of carbonic acid, and the liquid assumes 
a very fine red tint without being decomposed. It is composed of 
Carbo My. Mare eOlotGll 6 atoms or equivalents, 
Hydrogen . . . 0.0470 Gis de 
Ory gent OMe eA ORS TEON NMS he “ 
The metagallic acid is of a brilliant black color, insipid, and inso- 
luble in water. Potash, soda, ammonia and glucina dissolve it easily. 
It expels the carbonic acid from the alkaline carbonates, and forms 
black precipitates in the most of the metallic salts. It is composed 
of 
Carbon . . . . 0.7310 12 atoms or equivalents, 
Hydrogen” . . |. 0.0298 6 “ cc 
Oxygen 5 9. +... 0.2392 ey aicc cc 
In an isolated state, it contains in addition, 1 atom of water.—Idem. 
3. Formic Acid, by Déperziner. (Ann de Ch. t. 52, p. 105.)— 
The following is the best process for obtaining it. Dissolve 1 part 
