54 JOURNAL OF THE 



recently that so gooi a material as the Mejillones guano has been 

 successfully used. For Dr. Pieper (Landw. Centralbl. 1873, 1, 371) 

 only a few years ago gave impetus to the use of this material. And 

 there are other phosphates equally as good, which so far defy alike 

 the chemist and the manufacturer. But with the ordinary grades 

 of Charleston rock one can predict the actual resul of treatment 

 within very narrow limits. It is the purpose of this article to dis- 

 cuss briefly the action of sulphuric acid on some grades of Charles- 

 ton rock. 



The rock was ground so that the whole of it passed a BO*^ seive. It 

 was then sampled and analysed. 



The analysis was as follows : 



Per cent. 



Moisture at 2I2^F 6.52 



Loss at red heat (COo restored) 3.83 



Insoluble silica 17. 84 



Soluble silica _ .10 



Carbonic acid _ .. .. 2.80 



Phosphoric acid __ 22.82 



Lime 33.60 



Ferric oxide, (Oxide of Iron) 11.56 



Aluminic oxide .00 



99.07 

 The amount of oxide of iron is greater than is usually found. 

 The formula used was: 



EXPERIMENT I. 



Rock . 1 200 lbs, 



Sulphuric acid, 47°B . ..1050 " 



Temp, of acid I40°F. (6o'C.) 

 in pan i8o'F. (82'C.) 

 Stirred 3 minutes and sampled direct from pan. 



To show the difference between the " calculated " and " found '• 

 ingredients the subjoined comparison is given : 



Calculated. Found. 



Per cent. Per cent. 



Moisture at 2I2°F.. 24.51 27.75 



Phos. acid sol. in water 9.30 8.53 



" insol. in water 2. 88 2.92 



" total.. 12.18 11.45 



