1814.] Philosophical Transactions, Partll. \S\Z. ^85 



scale to be depended on as exact, Sir H. Davy ascertained, that it 

 is a compound of one volume of azote and four volumes of chlo- 

 rine, or by weight of 



Chlorine 90-9 10 or 4-525 x 4 - 



Azote 9060 or 1 -803 



100-000 



11. Experiments on the Production of Cold by the Evaporation 

 of Sulphuiet of Carbon. By Alexander Marcet, M.D. F.R.Sr 

 one of the Physicians to Guy's Hospital. Dr. Marcet has ascer- 

 tained, that a greater degree of cold is produced by the evaporation 

 of sulphuret of carbon than by that of any other liquid. If the 

 bulb of a small spirit of wine thermometer be surrounded with lint 

 wetted with alcohol of sulphur, it sinks in the open air even in 

 summer nearly to zero. If it be introduced into the receiver of an 

 air pump, and a vacuum be made, the thermometer in a few mi- 

 nutes sinks to — 70° or — 80° j and if a tube containing mercury 

 be substituted in its place, that metal freezes very speedily. 



12. On a Saline Substance from Mount Vesuvius. By James 

 Smithson, Esq. F. K. S. This saline substance was thrown out of- 

 Vesuvius about the year 1792, and was examined by Mr. Smithson 

 in 1794. A more recent examination, described in the paper, but 

 not susceptible of abridgment, enabled him to ascertain its com- 

 position to be as follows : 



Sulphate of potash 7*14 



Sulphate of soda 1-86 



Common salt 0*46 



Sal ammoniac 1 



Muriate of copper [• 0*54 



Muriate of iron j 



10-00 



There was mixed vvitli it also some submuriatc of copper and 

 aubmuriate of iron. 



13. Some Experiments and Observations on th.e Substances pro- 

 duced in dilfeient Chemical Processes on Fluor Spar. By Sir 

 Humphry Davy, LL.D. F.R.S. V.P.K.l. This paper is very 

 different from the one read to the Royal Society on the Sth July, 

 1813 ; being niucli fuller, and containing a greater number of ex- 

 perimental details. 'J'hree substances have been for a considerable 

 time known to cliemists; namely, fluoric acid, silicated fluoric 

 acid, and Huoboric acid. The two first of these were discovered by 

 Schcele ; the last by Gay-Lussac and Thenard. Sir H. Davy'i 

 attention was drawn to this suliject Ijy a letter from M. Ampere, 

 who drew a comparison between tkioric acid and muriatic acid, and 

 endeavoured to show that the former like the latter was a com- 

 pound of hydrogen, and an unknown supporter of tombustion, for 



