128 Dr. E. Divers on the Diammonic Carbonate. 



tion of some of the salt, attended with the liberation of water, and 

 a deposition of the little-soluble acid carbonate on the surface of 

 the cake and in the pores of the paper. Not to lose too much 

 ammonia, the salt was collected in a slightly damp condition. 

 Sample III. was the same preparation as II., but was subjected to 

 a much longer process of drying, with, however, little apparent ad- 

 vantage. 



The substance IV. was the semicrystalline solid which is left 

 when the commercial carbonate is first treated with ammonia so- 

 lution. It was dried as was II., and behaved similarly, except 

 that it had no lustre to lose. Lastly, V. was the crystalline form 

 of the carbonate obtained by dissolving the commercial carbonate 

 (freed from adhering acid carbonate) to saturation in water 

 mixed with some strong solution of ammonia, and then keeping 

 the solution cool for a couple of hours in ice. It was not pre- 

 pared with much dispatch for analysis; and the numbers ob- 

 tained show evidence of marked decomposition having occurred. 

 In sample I., which appears to have contained over 2 per cent, 

 moisture, the ammonia will be seen to have been almost exactly 

 in quantity equivalent to that of the carbonic anhydride. The 

 portion of II. destined for the determination of the ammonia was 

 spoiled. 



If either of the forms of the carbonate be leisurely pressed 

 with free exposure, so long as it damps fresh paper it becomes 

 the dry hydric amnionic (or acid) carbonate. One specimen 

 thus obtained was analyzed. 



The ammonia was determined by standard solutions of sul- 

 phuric acid and soda, the carbonate being dropped from the 

 weighing-tube into a flask containing a small excess of the acid 

 diluted, the solution boiled and shaken to get rid of all carbonic 

 anhydride, and then the soda added to neutralization. The 

 carbonic anhydride was estimated in the direct way, after its ex- 

 pulsion by hydrochloric acid and passage over fused calcic chlo- 

 ride and blue-vitriolized pumice, by combining it with soda-lime 

 in a U-tube. The apparatus was arranged and the operation 

 performed with the precautions prescribed in Fresenius's 'Quan- 

 titative Analysis/ 



Sample I. — "7877 grm. gave "2948 grm. carbonic anhydride; 

 •74565 grm. gave '21318 grm. ammonia. 



Sample II. — *7063 grm. gave *2715 grm. carbonic anhydride. 



Sample III. — '7172 grm. gave *2857 grm. carbonic anhydride; 

 •5483 grm. gave *1547 grm. ammonia. 



Sample IV. — 1*05965 grm. gave "4042 grm. carbonic an- 

 hydride ; '4627 grm. gave *12886 grm. ammonia. 



