Ictii'iBcn some Kinds of Fhi'uh, 1 59 



stratum of ammoni.i expels it around, and forms a circle. 

 This shows, acicording to Draparnaud, that the expansive 

 force of spirit of wine is grtiater than that of ammonia. 



But I remark that ammonia has no attraction of surlace, 

 or at least very little witli the bottom of vessels, and, on 

 the contrary, th.it alcohol has a great deal. If a drop of. 

 annnonia be poured on a porcelain saucer, or on a piece of 

 glass, and one of spirit of wine, the former remains con- 

 centrated, and the other dilates itself. Tt)is is the reason 

 xvhy spirit of wine expels ammonia on the bottom of vessels, 

 and that ammonia docs not expel spirit of wine. 



Moreover, if the expulsion of the annnonia depended on 

 the mechanical impression of the en^anations of the spirit 

 of wine, it ought scarcely to manifest itself; for the force 

 of the emanations of the spirit of wine ou'/iu to be weak- 

 ened by the force of the emanations of the ammonia, but 

 it manifests itself with the same promptitude as that of 

 water. It is observed also, that some fluids almost equally 

 volatile and odoriferous expel each other when applied iji 

 succession to the same surface. For example, essential oil 

 of turpentine expels naptha, and ether cxp.'ls essential oil 

 of turpentine. 



If the opposite force? destroyed each other, how could 

 this happen ? Eut the case is so, because e.:;sentKd ol! of 

 turpentine has more attraction of surface than naptha, and 

 ether more than essential oil of turpentine. 



But there is one observation of Draparnaud whicli de- 

 serves to be discussed. He has remarked that ammonia 

 f.xpels oil from the surface of vessels, though it expels nei- 

 ther water nor spirit of wine, I have remarked also, that 

 the approach alone of a drop of anmionia to the surface of 

 oil, manifests there an evident commotion, as if it were 

 breathed upon. It appears then that the emanations of 

 ammonia render themselves by these means manifest to the 

 sight, that is to say, in con-secjuence of the expulsive: force 

 or mechanical rthock of the oil. 



I do not pretend, nor have ever pretended, th.it there 

 can l)e no emanations of volatile bodies capable of render- 

 ing themselves scn-iible to the sight in this sense, but Onlv 

 to show ihat se\er.d phamomena which are considered as 

 the elfccts of repulsion, occasioned by the expansion of 

 volatile bodies, do nut depend on that cause, but are the 

 cflects of attraciioii of surface, and that there are no 

 means of rendering the ciuanations of oiiorifcrous hodie.^ 

 •cnsible to the sight, ai^ lica* digi Prcvost Lhjnks. f'liit be- 

 fit re 



