or Normal Carbonate of Ammonium. 127 



lous paper) it becomes a white powder of the acid carbonate, 

 weighing little more than half the original substance — the mat- 

 ters volatilized, therefore, being not only ammonia and water, 

 but also a good deal of the entire salt or its constituents. Not 

 only do the crystals become damp in the open air, but also, and 

 rapidly, when they are in closed vessels. 



The diammonic carbonate in the same crystalline condition 

 may also be obtained by dissolving the commercial salt to satu- 

 ration in water and then passing ammonia gas through the so- 

 lution kept cool. A moderately strong aqueous solution of the 

 new salt, cooled in ice, does not crystallize ; but when treated with 

 ammonia gas, the salt crystallizes out from it. By digestion after- 

 wards in the ammoniacal liquor the crystals gradually disappear, 

 and do not return when the liquid is cooled again to 0° C. Gently 

 heated in a closed tube, the crystals melt to a transparent liquid, 

 which volatilizes and forms a semicrystalline moist sublimate. 

 If the fused mass be cooled, it gradually solidifies to a mass of 

 prisms ; this mass, and most of the sublimate, spontaneously 

 volatilize when the tube is kept open ; at least they did so on 

 the occasion in which they were thus tried. 



To prepare the salt for analysis, it was rapidly deprived of the 

 bulk of the mother-liquor by draining on bibulous paper, and 

 then submitted to moderate pressure between fresh layers of 

 paper. In the case of sample I., after draining the crystals on 

 paper, they were enclosed in a small close glass chamber (ex- 

 temporized for the purpose) and packed tightly between bibulous 

 paper, and the whole was then left for some time surrounded with 

 ice. The vessel had to be opened from time to time to renew the 

 paper and break down the flakes of crystals ; but these operations 

 were performed with all possible expedition. When the drying 

 appeared to be complete, the soft crystalline cake of still lustrous 

 crystals was removed, pressed for a moment firmly between a 

 fresh fold of paper (no distinct damping of which was observed), 

 and then rapidly transferred to weighing-tubes and forthwith 

 analyzed. By the time the substance was in the tubes it had 

 lost much of its crystalline lustre, and began to be slightly adhe- 

 rent from acquired dampness, so rapidly does the salt change. 



Sample II. was not enclosed in the glass chamber and kept 

 cool by external cold ; but the active volatilization of its highly 

 ammoniacal mother-liquor maintained for a time a sensibly low 

 temperature in the mass. Some difference in behaviour during 

 the drying was observed, in consequence of this different arrange- 

 ment. After a few changes of paper little progress seemed to 

 be made in the drying ; and besides, the paper began to adhere 

 somewhat closely to the cake, which also lost most of its lustre. 

 The cause of these phenomena was undoubtedly the decomposi- 



