190 



were brought in, in the first cargo, which will account for the large 

 amount of sand in the subjoined analysis. Only the ground guano 

 was thus sent to me, so that the analysis represents the commercial 

 article, not a selected specimen. The actual guano contains only 

 about 0.5 per cent, of siliceous matter. 



The unusual quantity of phosphoric acid, contained in this sub- 

 stance, attracted attention, and many analyses were made of the new 

 guano. The habit of calculating the phosphates in these Mexican 

 guanos, as bone earth, or tribasic phosphate of lime, led some che- 

 mists into grievous errors. The new material was, in one breath, 

 called a super phosphate of lime, and in another, said to contain from 

 seven to eleven per cent, o^ free phosphoric acid. In common with 

 other chemists of Baltimore, on the first importation of this guano, I 

 made an analysis of it, and found it to contain a large proportion of 

 phosphates, but expressed no opinion as to their composition. At last, 

 however, hearing so much said about the soluble phosphoric acid in 

 this substance, I examined it more carefully, and found but little of 

 this acid soluble in water, and none of it/ree. I obtained the follow- 

 ing results : 



The proportions of the phosphates vary in difierent samples. Thus, 

 in one specimen, recently examined, there was a very small propor- 

 tion of magnesia and 4.23 per cent, of phosphate of iron. 



The organic matter was partly soluble in hydrochloric acid, and 

 partly in potash. A cursory examination of it seemed to indicate 



