124 Mr. Denham Smith on the Corn-position of 



termed "stones" by the labourers: when broken, this variety 

 presents a crystalline fracture, resembling a fused salt of a 

 brown colour; it appears to exist in large quantities in the 

 guano when imported, for at the warehouses whence I ob- 

 tained my samples, I was told that at least a hundred tons of 

 it had been picked from the guano they had hitherto sent out 

 for consumption. For the sake of distinguishing this variety, 

 I shall term it " Saline Guano," whilst the second kind I shall 

 call " Concrete Guano." 



After a preliminary qualitative examination of these varie- 

 ties of this manure, the utility of another and probably more 

 exact mode of estimating ammonia than by condensing the 

 gas in hydrochloric acid and evaporating the solution to dry- 

 ness, and a more oeconomical and less troublesome plan than 

 by a salt of platina, became obvious. I therefore had recourse 

 to an indirect method of analysis, that of estimating the am- 

 monia from the quantity of carbonate of barytes oV)tained. I 

 preferred a salt of barytes to any other substance forming a 

 true neutral carbonate, on account of the high atomic number 

 of barium, and its consequent capability of expressing with 

 exactness the quantity of ammonia, as well as the great deli- 

 cacy of a salt of barytes in evidencing the existence of carbo- 

 nate of ammonia, for which purpose this substance is superior 

 to a salt of lime, or even to lime water. 



The point which appeared most likely to occasion error 

 was, that the carbonate of ammonia might not be obtained as 

 a true neutral carbonate ; as a basic carbonate would of course 

 vitiate the results, and the frequency of the occurrence of 

 such combinations we all know since the publication of Rose's 

 excellent paper on this subject. Experiment showed that the 

 neutral carbonates of potash and soda, distilled with a solution 

 of an ammoniacal salt, afforded a basic carbonate of ammo- 

 nia, the solution being alkaline after a salt of barytes had been 

 added until no further precipitate fell, and that a current of 

 carbonic acid gas produced a precipitate in such a solution 

 when filtered. The acid carbonates of soda and potash an- 

 swered well enough where the ammonia existed in small quan- 

 tities, but when a large proportion of the volatile alkali was 

 present in the liquor subjected to distillation, the distilled so- 

 lution evidently contained a basic carbonate, as when the or- 

 dinary carbonates of soda and potash were used. It now re- 

 mained to be proved whether the acid carbonates of ammonia 

 would afford correct results. To determine this point, .59grs. 

 of sesquicarbonate of ammonia, taken from the centre of a lump, 

 were dissolved in cold water and precipitated by excess of ni- 

 trate of barytes, the solution being exposed to the air in an open 



