Dr. Odling o?i a Theory of Condensed Ammonia Compounds. 455 



Thus, on the one hand, in consequence of the continual ab- 

 sorption of aqueous vapour, the film can never at any phase of 

 its existence become very thin ; and, on the other hand, the ratio 

 between superficial viscosity and tension remains great enough 

 to render the rupture of the film difficult, until the proportion 

 of water assimilated by it has become very great. 



I conclude by showing that in relation to the ready develop- 

 ment of large films and the persistence of them, the part played 

 by cohesion is subsidiary to that played by internal viscosity. In 

 fact, for different liquids, the cohesion is known to vary in the 

 same direction as the coefficient of the sum of the curvatures in 

 the expression for the capillary pressure — a coefficient which, 

 according to the researches of M. Hagen and M. Dupre,is nothing 

 else than the tension ; and since this latter is much weaker in 

 soap-water than in pure water, the same is necessarily true for 

 the cohesion also ; but, notwithstanding, solution of soap yields 

 enormous bubbles, while water does not yield any. 



LV. Note on a Theory of Condensed Ammonia Compounds. 

 By William Odling, M.B., F.R.S.* 



THE unit of ammonia, N H 3 , has the well-known property 

 of combining with the unit of hydrochloric acid, HC1, to 

 form a unit of the more complex body sal-ammoniac, HC1,NH 3 . 

 Hypothetical methylene being regarded as the analogue of 

 ammonia, chloride of methyle will be the hydrochloride of me- 

 thylene, corresponding to sal-ammoniac or hydrochloride of am- 

 monia, 



HC1,CH 2 , HC1,NH 3 . 



But this chloride of methyle or hydrochloride of methylene is 

 known to be the first term of a series of compounds, the earlier 

 terms of which are formulated below. In a parallel column are 

 written the formulae of what, if they existed, would form a similar 

 series of sal-ammoniac compounds : — 



Chloride of methyle 



HC1,C H 2 



HC1,N H 3 



„ ethyle 



HC1,C 2 H 4 



HC1,N 2 H 6 



„ propyle 



HC1,C 3 H 6 



HC1,N 3 H9 



„ butyle 



HC1,C 4 H 8 



HC1,N 4 H 12 



„ amyle 



HC1,C 5 H 10 



HC1,N 5 H 15 





&c. 



&c. 



Substituting an equivalent of metallic chloride for chloride of 

 hydrogen in the sal-ammoniac series, we have the following 



* Communicated by the Author, 



