of the Slow Combustion of Ether. 69 



of the subject quite clear, but I think upon consideration may 

 be satisfactorily explained. In the former, a predisposing affi- 

 nity exists between all the ingredients obviously tending to 

 such an arrangement, resulting from the combined attraction of 

 the mercury for oxygen, and of the acetic acid for the pro- 

 toxide, but in the latter no such predisposing force can exist. 

 When muriatic acid is put to the mixture of mercury and per- 

 oxide, a double decomposition takes place ; the two propor- 

 tions of oxygen in the oxide combine with two proportions of 

 hydrogen derived from the acid, and water and a bichloride are 

 formed, the metallic mercury remaining untouched : for, al- 

 though we can readily enough conceive in the former instance 

 that the play of affinities should produce the permanent ar- 

 rangement of the proto-acetate of mercury, it is impossible 

 to imagine that any predisposing affinity should determine the 

 composition of protoxide of mercury, and at the same time 

 its decomposition, as must have been the case if protochloride 

 of mercury had been formed from the mixture of metal and per- 

 oxide ; that is to say, protoxide of mercury must have been 

 formed by the action of the metallic mercury upon the peroxide, 

 merely for the purpose of being again decomposed by the 

 agency of the acid, the whole arrangement being determined 

 by the affinity of two substances which in point of fact did not 

 exist. 



I believe that it is the general opinion that the red preci- 

 pitate is a more impure preparation of the peroxide of mercury 

 than the oxide per se ; but these experiments would seem to 

 prove the contrary. Certain it is, that in medicine the former, 

 which is of very low price, is not considered to answer the 

 same purposes as the latter, which is a costly drug. Might 

 not a due mixture of metallic mercury with the former assimi- 

 late the properties of the two ? It is right to mention that the 

 oxides which 1 employed were obtained from Messrs. Allen 

 and Co. Plough-court, the accuracy of whose preparations are 

 well known. 



But to return to the immediate oI>jcct of this paper. 1 en- 



