Rankine on the Thei^modynamic Theory of the Steam-engine. 71 



the same composition as ninaphthylamine. But a ^^Pfjfif ^^ J?"?" 

 parison of the properties of the two bodies excludes any idea of their 

 bein- identical: The formulae of nitrosophenyhne and nitrosouaph- 

 tvlbe have not as yet been finally established by the analysis of their 

 compounds, these substances, like colouring matters m general 

 ESof an indifferent character. It is probable that they are formed 

 by the association of several molecules, a supposition which receives 

 considerable support from the discovery of ninaphthylamme. 



The formatiin of ninaphthylamine promises to add considerably 

 to the number of nitro-derivatives of the aromatic monammes. lo 

 each of these substances probably corresponds a nitrous and a nitric 

 substitution-base, but as yet we are unacquainted with a smgle one 

 in which both derivatives are known, as shown by a glance at the 

 groups best examined. 



Phenyle Group. Naphtyle Group. 



Phenylamine. . . . ''h' I N, Naphthylamine H V N. 



C, (H, NO,) j N, Ninaphthyl-C- (H^ NO,) 1 ^ 

 Unknown.. H V ^^i^e ^ f 



... V, ,C,,(H,N0J1 ^-(^W^^^Mxr 



Nitrophenyl- ^'^ H I N, Unknown H V N. 



amine. . . = H ) H J 



"On the Thermodynamic Theory of Steam-engines with dry 

 saturated Steam, and its application to practice." By W. J. Mac- 

 quorn Rankine, C.E., LL.D., F.R.S.S.L. & E. 



In 1849 it was demonstrated, contemporaneously and mdepend- 

 entlv by Professor Clausius and the author of this paper, from the 

 laws of thermodynamics, that when steam or other saturated vapour 

 in expanding performs work, and receives no heat from without, a 

 portion of it must be liquefied. ^ j i, ,„„f;„oi 



That theoretical conclusion has since been confirmed by practical 



^^TheTrincipal effect of the "steam-jacket" invented by Watt is to 

 prevent that liquefaction. ., ,, .•- • *i,„ 



The presence of liquid water in any considerable quantity in the 

 cylinder of a steam-engine acts injuriously, by taking heat trom the 

 steam while it is being admitted, and giving out that heat to the 

 steam which is about to be discharged. Most of the heat so trans- 

 ferred is wasted. p .1 1 ^ t ^ 



The only exact thermod^jnamic formulae for the work ot steam 

 hitherto published (by the author in the Phil. Trans 1854, and by 

 Professor Clausius in the Philosophical Magazine for 18^6), are 

 adapted to steam which receives no heat m expanding. 



The present paper, after recapitulating the general equation of 

 thermodynamics, and the special formulae for the pressure, volume, 

 and latent heat of steam, proceeds to the investigation ot the exact 



