200 
POPULAR SCIENCE REYIEW. 
colour is developed, especially on application of a gentle heat. Of course in 
using the above tests to show earthy carbonates in water, care must he taken 
that no alkali is present. — Vide Chemical News, Dec. 27. 
The Gallic Fermentation has been very fully investigated in a memoir 
read before the French Academy, by M. Van Tieghem. This chemist 
adopts the following conclusions : — 1. Tannin does not undergo the meta- 
morphosis when protected from the atmosphere. If a series of flasks he 
filled entirely with a solution of tannin or a filtered infusion of nut-galls, 
and placed in vacuo for 24 hours, then saturated with carbonic acid, care- 
fully corked and heated, and finally sealed while hot, the solution will 
remain unchauged for any length of time. The transformation of tannin 
into gallic acid is not, then, due to the pre-existence of a soluble ferment. 
2. Tannin does not undergo metamorphosis by simple contact with the air. 
A solution of tannin introduced into a series of flasks drawn out at the neck 
and curved, boiled for some minutes, and left in a quiet place at a tem- 
perature of about 25° C., will remain unchanged for any length of time. 
3. For tannin to undergo the metamorphosis, the development of a species 
of fungus in the solution is essential and sufficient. The gases composing^ ; 
the atmosphere alone effect no change, but the atmosphere carries to the ' 
solution spores, and these require for their germination oxygen. Under j 
these influences the tannin splits up into gallic acid and glucose, the ele- j 
ments of water becoming fixed. — Vide Comptes Rendus, Jan. 6 . I 
Bleaching on the Continent. — It is stated by a contemporary that the old | 
bleaching powder has given way abroad to a combination of the perman- t 
ganates and sulphate of magnesia. This method is cheaper and more effi- 1 
cient than the old one. j 
Manufacture of Sodic Carbonate. — The following method has, we believe, j 
been attempted and found tolerably successful. Steam and the vapour from ^ 
salt are allowed to operate on silica. The latter is converted into a silicate | 
of soda. By the addition of lime, caustic soda is separated, and by adding- j 
carbonic acid this is converted into carbonate of soda. ^ 
Viridinic Acid may be obtained direct from coffee by pulverising the j 
beans, extracting the fat with alcohol, and then exposing them to the air. * 
In a few days they become covered with a green substance, which may be | 
removed with alcohol and acetic acid. — ^Vide Ann. Chem. Pharm. cxliii. 5 
An economic source of Acetylene has been suggested by Herr Bieth, in the | 
Zeitschrift fur Chemie [N. F. 3, p. §98]. In fact, when the flame of a. ] 
Bunsen’s lamp burns below so that it comes within the tube, a large amount I 
of acetylene is evolved. The gases may be collected by a funnel connected i 
with an aspirator. As much as 100 grammes of the silver compound of I 
acetylene have been obtained in twelve hours from a single burner. i 
The Identity of Ozone. — It has so often happened lately that the question 
has been asked — Is the substance in the air which acts on the tests Ozone P 
that we are glad to find a satisfactory answer given to it by Dr. T. Andrews, 
F.R.S. In a paper on the subject which he published in one of the late , 
numbers of the Proceedings of the Royal Society, Dr. Andrews gives many 
reasons for believing that the atmospheric substance is really ozone. Heat ■■ 
Dr. Andrews regards as furnishing the most convincing testimony. In a j 
communication to the Philosophical Transactions for 1856 he proved that ] 
