Dr. E. Divers on the Diammonic Carbonate. 125 



results which have been evolved from the general equation (2) 

 without the aid of any subsidiary hypothesis with regard to the 

 nature of the law of pressure, by the simple application to (2) of 

 the ordinary process for the integration of partial differential equa- 

 tions of the second order involving two independent variables*. 



If the fact of the expression for the pressure containing an 

 arbitrary function, thus causing three arbitrary functions to enter 

 into the complete solution of the problem, occasions surprise, I 

 may observe that it may be shown a priori that such must be the 

 case. 



6 New Square, Lincoln's Inn, 

 July 7, 1868. 



XVI. On the Diammonic Carbonate, or Normal Carbonate of Am- 

 monium. By Edward Divers, M.D., F.C.S., Lecturer on 

 Natural Philosophy, Charing Cross Hospital^, 



IT is now nearly thirty years ago since H. Rose wrote, in his 

 classical memoir on the compounds of ammonia with car- 

 bonic acid J, "the neutral anhydrous carbonate of ammonia 

 cannot be combined with the quantity of water sufficient to con- 

 vert the ammonia into oxide of ammonium." The carbonates 

 of ammonia have since been reinvestigated by Deville § ; and he 

 admits the existence of only two crystalline combinations — the 

 tetrammonic dihydric tricarbonate (or true sesquicarbonate), and 

 the amnionic hydric carbonate (or bicarbonate). 



Resting on the authority of these distinguished chemists, the 

 text-books tell us that the carbonate of ammonium cannot be 

 isolated. I have now to announce that the normal or diammonic 

 carbonate can be prepared in the simplest manner imaginable. 

 I must say that, with the above assertions before me, I was much 

 pleased to succeed very easily in my efforts to form this body ; 

 but I certainly was not astonished, because comparatively recently 

 it has been shown by Dr. Hofmann that two bodies whose place 

 is little beyond the threshhold of chemistry (formic aldehyde and 

 formamide), and which it was said could not be produced, are 

 actually to be prepared in the most ordinary manner. 



Diammonic carbonate is formed by treating the commercial 



* The truth of equations (16) may be readily verified, observing that, in 

 virtue of the value there given for p, (2) can be put under the form 



q _ du , x'( u ) du . « dp . cc? dp 

 ~ dt ~W dx f dt T)p~ 2 <k' 

 t Communicated by the Author. 

 X Pogg. Ann. vol. xlvi. p. 373. 

 § Ann. de Chim. S. 3. vol. xl. p. 87. 



