232.Gas Blow-pipe.— Decomposition of Sulphate of Soda by Iron. 
science and artisans, instruments in common use may be obtained 
at less cost than at present, and sufficiently proof against humi- 
dity and the juices of fruits. 
Foreigners, as well as natives of France, are allowed to com- 
pete for the prize ; but in the event of its being gained by a fo- 
reigner, the Society are to have the property of the process so 
far as regards its adoption in France. 
XXXVII. Intelligence and Miscellaneous Articles. 
GAS BLOW-PIPE. 
To Mr. Tilloch. 
Paris, Feb. 15, 1819. 
Sir, — Wauen at Florence I had some conversation with the 
Marquis Ridolfi, on the results of the action ef the compressed 
gases on the earths. I cannot doubt from his assurance, that he 
has repeated Dr. Clarke’s experiments with success. The me- 
tallic grains were almost microscopic, yet exhibited an action 
sufficiently determined for their metallic character, such as effer- 
vescence in contact with water, &c. 
The Marquis was good enough to show me an improvement 
he has made in this instrument. I submit a sketch of the ap- 
pendage to you (Fig. B, Plate II.) The united gases, prior to 
ignition, pass through mercury contained in a small cistern (of 
iron) exterior to the reservoir. With this arrangement he has 
never experienced accident, though he has had explosion within 
the safety cell, even when supplied with folds of wire-gauze and 
with water. 
Numerous experiments have convinced me that the gases be- 
fore their issue, have in consequence of humidity (from traversing 
the water in the safety cistern) their intensity attenuated. Allow 
me therefore to suggest that they should pass a jointed ball sup- 
plied with dry muriate of lime before they escape from the ori- 
fice. I have the honour to be, sir, 
Your very humble servant, 
(Signed) J. Murray. 
DECOMPOSITION OF SULPHATE OF SODA BY IRON. 
January 8, 1819. 
Sir,—By inserting the following in your valuable Philosophical 
periodical publication, you will much oblige 
Your obedient servant, 
To Mr. Tilloch. Joun CHARLES PEARSON. 
About three months since, a Mr. Henry Jephson called on me 
and requested to know if I would sell him, for a friend, a large 
quantity of bleacher’s refuse which was in my possession. (It 
was 
