1818.] Edinburgh Transactions, Vol. VIII. Part II. 379 



in the gaseous state, and of course of being separated from it 

 without depriving this acid of its gaseous state; and according 

 to their calculations, the water which thus constitutes an essen- 

 tial part of muriatic acid amounts to about ^-rh of the weight of 

 the compound. According to this explanation, chlorine is a 

 compound of one atom of oxygen and a certain unknown sub- 

 stance which has never yet been obtained in a separate state. If 

 we add an atom of hydrogen to this compound, it unites with the 

 atom of oxygen, is converted into water, and this water combining 

 with the unknown basis, converts it into muriatic acid gas. Sir 

 Humphry Davy explained the fact in another and a much sim- 

 pler manner. According to him, chlorine is a simple (that is to 

 say, an undecompounded) body. An atom of it has the property 

 of combining by combustion with an atom of hydrogen, a*id of 

 forming muriatic acid. Gay-Lussac and Thenard have adopted 

 this explanation, and abandoned their own. Indeed they sug- 

 gested it in their original publication ; and Gay-Lussac informs 

 us that he had embraced it from the first, and that he had always 

 from that time taught it in his lectures. 



According to the first of these explanations muriatic acid is a 

 compound of ±th water and -5-ths of an unknown substance, 

 which constitutes the acid of the muriates : according to the 

 second it is a compound of chlorine and hydrogen. 



Dr. Murray, of Edinburgh, is almost the only person in this 

 country who has supported the first or old opinion. A controversy 

 took place several years ago in Nicholson's Journal, between 

 him and Dr. John Davy, on this subject ; the former supporting 

 the old, the latter the new opinion. This controversy was 

 carried on by both with much ability, and led to the discovery of a 

 variety of new and interesting facts ; but it terminated as almost 

 all controversies do : both combatants retained the original 

 opinions with which they had set out, and both of them boasted 

 of having gained a complete victory, and of having. established 

 his own opinions by the most satisfactory arguments. 



It occurred to Dr. Murray that muriate of ammonia might be 

 employed to furnish an evidence on the one side or the other 

 which should be decisive. According to the old view of the 

 subject muriatic acid contains ^th of its weight of water : when 

 it unites to ammonia this water ceases to be necessary to its 

 constitution, and may, therefore, be obtained in a separate state. 

 Suppose we mix equal volumes of dry muriatic acid and amino- 

 niacal gases, they combine and constitute sal-ammoniac. Now 

 a volume of ammonia approaches to half the weight of a volume 

 of muriatic acid ; therefore, dry sal-ammoniac, formed by the 

 union of the gases, must contain about the 6th of its weight of 

 water ; therefore, 100 grains of sal-ammoniac made in this way, 

 if the old theory be true, must contain nearly 17 grains of water. 

 Dr. Murray formed sal-ammoniac by uniting the gases ; he ex- 

 posed it to heat, and he obtained, in eveiy case, a sensible 

 quantity of water : this result, in his opinion, decided the con- 



