148 PROFESSOR TRAILL ON BERG-MEAL, OR MINERAL FLOUR. 



substance, with results so nearly similar, that I consider 22 per cent, as the real 

 proportion of this mineral destructible by a red heat : and as it had first been 

 carefully dried, that number may probably be fairly considered as an approxima- 

 tion to the quantity of organic matter which it contains. 



C. 



1. 78 grains of the incinerated Berg-Meal (B. 1.) were digested with sulphuric 

 acid, to which distilled water was added, and the digestion continued for 48 hours. 

 The clear liquid was drawn off by the pipette, and the residue, largely diluted 

 with distilled water, was thrown on the filter, when it was well washed, dried, 

 heated to redness in a platinum-crucible, and weighed while still warm. It 

 =71.13 grains, or 8.87 grains had been taken up by the acid. 



2. Similar results were obtained by digestion with undiluted hydrochloric 

 acid, which became of a pale straw-colour. The residue very nearly agreed with 

 the above carefully performed experiment (C. 1.) 



D. 



1. 78 grains of the incinerated mineral were digested with hydrochloric acid 

 (in C. 2.) diluted with distilled water for 48 hours. To the solution neutral ben- 

 zoate of ammonia was added until all precipitation had ceased. The liquid 

 became turbid and yellowish-brown. Next day the precipitate, in bulky flocks, 

 lay at the bottom of the vessel, leaving the supernatant liquid colourless and 

 transparent. The addition of more of the test produced no further change in the 

 liquid ; and therefore I conclude that all the iron had been thrown down. The 

 clear liquor was withdrawn by the pipette ; the rest was thrown on the filter and 

 well washed. 



2. I found it impossible to separate all the precipitate from the paper, but 

 having dried the part of the filter stained with the iron, I burnt it on a platinum 

 dish, moistened the ash with nitric acid, and exposed the whole to a strong red 

 heat. The residue was a reddish-brown oxide of iron which weighed 0.15 grain. 



D. 



1. To separate the alumine, 78 grains of the incinerated Berg-Meal were 

 digested in hydrochloric acid as before ; and when a diluted clear solution was 

 obtained, it was precipitated by carbonate of ammonia : a gelatinous greyish pre- 

 cipitate resulted, which adhered to the filtering paper. The greatest part of it 

 was removed before it was quite dry. This, when exposed to a red heat, had a 

 reddish-yellow colour ; and it was found that the iron was precipitated with the 

 alumine. The filter was burnt and treated as before (D. 2.), and the whole 

 together weighed 5.46 grains. The former experiment (D. 1.) had shewn that 

 the quantity of oxide of iron = 0.15 grain, and, therefore, the real quantity of 

 alumine in the Berg-Meal = 5.31 grains. 



2. The examination of the residual liquid, after the separation of the iron, 



