1818.] Royal Society of Edinburgh. 149 



While each of these elements, oxygen and hydrogen, commu- 

 nicates acidity, their combined action seems to do so in a still 

 higher degree. Sulphur with hydrogen forms a weak acid ; with 

 oxygen, another acid somewhat stronger; with oxygen and 

 hydrogen, one of still greater power. Nitrogen with hydrogen 

 forms a compound having no acidity ; with oxygen in two pro- 

 portions, it forms oxides ; with oxygen and hydrogen, a powerful 

 acid. Carbon with hydrogen forms compounds which are not 

 acid ; with oxygen, in one proportion, it forms an oxide ; in 

 another, a weak acid ; with oxygen and hydrogen, the different 

 vegetable acids which are of much superior strength. 



This explains the apparent anomaly which appeared in the 

 old doctrine with regard to oxymuriatic acid, that it is a weaker 

 acid than the muriatic, though it has received an additional por- 

 tion of oxygen. It is so precisely, as sulphurous acid is weaker 

 than sulphuric. The proper points of resemblance are the sul- 

 phurous acid with the oxymuriatic, and the sulphuric with the 

 muriatic. It was shown that oxymuriatic acid has a stricter 

 analogy to sulphurous acid than to any other body ; and that any 

 deviation from this analogy arises from the large proportion of 

 oxygen which the former contains. 



The relations of iodine, the analogy of which, in some 

 respects, to those of chlorine, has chiefly given predominance to 

 the new doctrine with regard to the latter, accords perfectly 

 with these views. The nature of the compounds of inflammable 

 bodies with chlorine accord also better with them than with 

 either of the other doctrines. And they serve to explain a 

 number of other facts connected with the action of acids and 

 their combinations. They afford, for example, a solution of the 

 difficulty which gave rise to the investigation — that of the pro- 

 duction of water in the action of metals on muriatic acid gas. 



Dr. Murray extended the same view to the constitution of the 

 alkalies. Alkalinity is, as well as acidity, a result of the agency 

 of oxygen ; the fixed alkalies, the earths, and metallic oxides, 

 which all contain oxygen as a common element, forming a series 

 in which there is no well defined line of separation. Ammonia 

 stands insulated ; it contains no oxygen, yet its alkaline properties 

 are energetic ; an anomaly which has led generally to the belief 

 that oxygen must exist in one or other of its constituent prin- 

 ciples. It may be explained, however, on a very different 

 principle. As hydrogen, like oxygen, communicates acidity, so 

 it may, like oxygen, give rise to alkalinity. Ammonia, therefore, 

 will be a compound, of which nitrogen is the base, deriving its 

 alkaline quality from hydrogen ; and hence stands in the same 

 relation to the other alkalies that sulphuretted hydrogen does to 

 the acids, li' the claim of the newly discovered principle in 

 opium to the rank of an alkali be established, it may stand in the 

 same relation to the others that prussic acid, or some of the 

 vegetable acids, do to tin- acids. 



