465 



us. They decompose the sulphuretted hydrogen, and their 

 liberated acid combines to form a fixed salt with any present 

 ammonia. Their action on the septic gases is, I apprehend, 

 very nearly alike in them all, in so far as two of the most 

 offensively odorous of these gases are concerned; and we have 

 no reason to suppose they exert any influence on the others, 

 beyond the power these fluids possess as antiseptics to sus- 

 pend further disengagement of them. The action between 

 the zinc and the putrid gases referred to will be, that a 

 portion of the neutral chloride will be decomposed, yielding, 

 with the sulphuretted hydrogen, an insoluble sulphuret of 

 zinc and hydrochloric acid; whilst with hydro -sulphate of 

 ammonia, the other foetid vapour, we have again a sulphuret 

 of the m.etal and hydrochlorate of ammonia. It may be said 

 in this case, in contradistinction to the other rival liquids, 

 that a part only of the salt used would be decomposed ; for 

 so soon as the acid is in excess, or free, the further action 

 upon any additional sulphuretted hydrogen present is sus- 

 pended; and that the only insoluble product is the sulphuret, 

 which, indeed, shortly by oxidation becomes itself a soluble 

 sulphate. In reply to this objection it may be urged, that 

 experiment shows the reaction to be such as to fix the sulphur 

 and remove the smell, although the agent be not continuously, 

 ad libitum, decomposed; and that though a larger quantity of 

 the fluid may be required to accomplish a given work, yet that 

 the object is attained. To the latter clause of the alleged 

 objection little defence can be offered ; for it does kSO happen 

 that all the salts of zinc, except the carbonate, are soluble, 

 and, pro tanto, pernicious to vegetation. Hence for the dis- 

 infection from stench of night-soil destined to agricultural 

 purposes, Burnett's fluid is not well suited. All the other 

 metallic salts, however, I believe to be open to this difficulty 

 in a variable degree ; and some of them, which are ordinarily 

 recognised as insoluble, become otherwise when exposed to 



