VARIETIES. 
379 
details, is obtained, the outlines of which can he laid hare by an etching- 
point capable of scratching the glass. If a glass plate, so marked, be rubbed 
in with printing ink, the outlines will be filled, and the ink will remain in 
them when the glass is freed from the coating of gum by means of water. 
The picture is then easily transferred to paper, which is to be laid on the 
plate and rubbed over with a paper-knife. — London Chem. Gaz., from Ar- 
chiv der Pliarm., Ixix. p. 301. 
On Gallic Acid Fermentation. By M. Bobiquet. — Gall-nuts contain; be- 
sides tannin and the several principles which have already been pointed out 
by chemists, pectose and pectase. The latter ferment, which exists both 
in the soluble and in the insoluble state, acts at the same time upon the 
pectose and upon the tannin, converting the first into pectine and the 
second into gallic acid. The presence of water and a temperature of 77° to 
86° F. are requisite for this reaction, which resembles in every respect the 
ordinary phenomena of fermentation. 
The ordinary tannin, which has been prepared with ether, contains suf- 
ficient pectase to pass spontaneously in the presence of water into gallic 
acid ; but if care has been taken to purify it, or if its solution has been 
simply boiled for a few minutes, the change no longer takes place. 
Synaptase, yeast, vegetable and animal albumen, and legumine have a 
very doubtful action upon tannin, and retard rather than accelerate its 
conversion into gallic acid. 
It is quite as easy to convert the pectine of fruits into pectic acid by 
means of the pectase obtained from gall-nuts, as to convert tannin into 
gallic acid with pectase separated from the juice of fresh roots, and espe- 
cially from turnips. — London Chem. Gaz., from Comptes Rendus, July 5, 
1852. 
On, the Manufacture of Gas from Wood. By Dr. Pettenkofer. — Two 
years ago, Dr. Pettenkofer showed by experiment, at a meeting of the Poly- 
technic Institute of Bavaria, that a very considerable amount of illumina- 
ting gas could be disengaged from 2 oz. of wood. Its practicability on a 
large scale has since been the subject of much doubt. The inventor's pro- 
cess is now in operation at Basle, and it is also, about to be introduced at 
Zurich, Stockholm and Drontheim. The process is said to be far less ex- 
pensive than the manufacture from fossil coal, and furnishes a gas which is 
free from sulphuretted hydrogen, and several useful collateral products, as 
charcoal, wood-tar and wood-vinegar. — London Chem. Gaz., from Central 
Blatt, March 10, 1852. 
On the Galbanum Plant. By F. A. Buhse. — The author states, that in 
his travels in Persia he discovered the plant which yields galbanum. In 
June, 1848, he found it on the declivities of the Demawend. It is a ferula, 
from the stalks of which a liquid issues abundantly, by the odor and nature 
