Litmus or Turmeric, ^c. 347 



I have ascertained that the white crystals which form 

 spontaneously, when silver coin is dissolved in nitric acid, 

 diluted no more than is necessary for the solution to pro- 

 ceed actively, give no trace of copper when redissolved. 

 May not this be a good preliminary step in refining that 

 metal, or for obtaining the nitrai either for lunar caustic or as 

 a test. 



I have observed that the strong nitric acid procured from 

 dry nitre, may be saturated with carbonate of ammonia in a 

 retort, and nitrous oxide procured forthwith, by distillation. 

 The salt produced is in the compact form. Instead of me- 

 tallic air-holders, I make use of bags, such as are made by 

 Pixii at Paris, (such as are called by him Reservoir en Bau- 

 druche) passing the gas through water by an apparatus, of 

 which I will send you a drawing as soon as convenient. I 

 find that bags of leather, soaked with boiled linseed oil, will 

 answer to hold the oxide gas. 



(fJ^This letter was written a twelve month ago. Th^ 

 facts have since been added in notes to the American edi- 

 tion — Ure's Nicholson's Dictionary. 



Art. XIX. — On the Combustion of Hydrogen in water — 

 being a new application of Harems Blowpipe. 



For the American Journal of Science. 

 Mr. Editor, 



I HAVE discovered, within three or four months back, 

 that if the flame, produced by the combustion of hydrogen 

 gas, issuing, in combination with oxygen, from the com- 

 pound blowpipe of Hare, be plunged below the surface of 

 a vessel of water, it continues, notwithstanding its submer- 

 sion in, and actual contact with, this element, to burn, ap- 

 parently with the same splendour as it does in the common 

 atmosphere. The only difference I am able to discover, is, 

 that when the flame burns in the water, it seems, so to 

 speak, to conglobate its figure ; — whereas in the air, the 

 shape it assumes, is that of a long slender conical pencil. 



You will readily believe that the water, which contains 

 within its bosom, a source of heat so abundant, as hydrogen 

 Vol. V....No. II. 45 



