466 NITRE. 



water it sinks the thermometer 19 during its solution. With ice it 

 produces a still greater degree of cold. It is used in hot countries for 

 cooling wine ; and the same portion of salt by evaporating and crys- 

 tallizing, may be used again and again. 



3. ACTION ON COMBUSTIBLES. The phenomena are brilliant 

 and instructive. 



(a.) Action of charcoal. If into melted nitre, charcoal powder be 

 thrown, it deflagrates ; and if 3 parts of nitre be employed to 1 of 

 charcoal, the action is very energetic.* 



(b.) The product of the detonation of charcoal and nitre is always 

 carbonic acid gas, mixed with nitric oxide and nitrogen, and probably 

 with oxide of carbon, and carbonate of potassa remains. If igni- 

 ted charcoal be held above melted nitre, it will burn with increased 

 brilliancy, owing to the disengagement of oxygen gas. 



(c.) Jlction of sulphur. Thrown into a red hot crucible, in the 

 proportion of 3 parts of nitre to 1 of sulphur, the latter burns away very 

 completely and rapidly ; the products are sulphuric and sulphurous 

 acid, sulphate of potassa, nitrogen and nitric oxide gas; the theory 

 is obvious. It has been already mentioned, that in the manufacture 

 of sulphuric acid a small quantity of nitre, usually about \ or {, is 

 added to the sulphur, and it was known only that the sulphur was 

 thus made to burn in such a manner as to form sulphuric rather than 

 sulphurous acid. Now it is known that the sulphur decomposes the 

 nitric acid of the nitre, by attracting such a proportion of its oxygen 

 as leaves nitric oxide, which is displaced by the sulphuric acid. The 

 nitric oxide meeting with oxygen in the air, forms red nitrous acid 

 vapor ; in the mean time the greater part of the sulphur has become 

 sulphurous acid ; the floor of the leaden chamber is covered with 

 water several inches in depth ; so that aqueous vapor, sulphurous 

 acid and nitrous acid, are present, in mixture. When the two latter 

 are mingled in a dry state, there is no decomposition, but with the aid 

 of water the nitrous acid transfers oxygen to the sulphurous acid and 

 converts it into the sulphuric ; it thus becomes again nitric oxide ; again 

 attracts oxygen and transfers it to the sulphurous acid ; and thus it 

 becomes a vehicle for oxygen between the atmosphere and the sul- 

 phurous acid. A small quantity of water enables the sulphurous acid 

 and the nitrous to unite and form a crystalline solid, as appears when 

 a drop of water is admitted into a globe containing the two agents in 

 a dry state ; the same thing is supposed to happen in the leaden 

 chamber, and the abundant water on the floor decomposing this com- 



* The Alchemists performed this deflagration, in a series of tubulated receivers, 

 connected with each other, and with a tubulated retort, into which, when red hot, 

 they projected their mixture of charcoal and nitre, immediately closing the aperture 

 of the retort; their apparatus often blew up, but it sometimes escaped, and they 

 then carefully collected the liquid condensed in the receivers ; this they called 

 clyssus of nitre, and imagined that it possessed the most wonderful properties in 

 alchemy. 



