PROFESSOR TRAILL ON BERG-MEAL, OR MINERAL FLOUR. 147 



the Swedish Berg-Meal seems to give it a marked superiority, as a substitute for 

 food, over all the earthy substances which are said to enter into the repasts of 

 of the Ottomacks, the Papuas, and the Negroes. 



ANALYSIS. 



A. 



This substance, which appears as a friable powder, is rather soft when rubbed 

 between the fingers; of a colour between greyish- white and wood-brown; blackens 

 at a red heat, giving out a faint, empyreumatic, ammoniacal odour ; and finally, 

 when the heat is increased, becomes of a pure white. 



1. It does not dissolve in water ; but, by long digestion in distilled water, it 

 loses about seven pey cent, of its weight, and imparts a yellowish tint to the fluid. 

 This water is quite transparent, even after concentration ; yet, on standing for 

 between two and three weeks, a few gelatinous flakes appeared in it, but I found 

 the quantity inappreciable. It also afforded a perceptible, but inappreciable quan- 

 tity of some muriate. 



2. When digested with strong sulphuric acid, it blackens, and a small portion 

 of earthy matter is dissolved. 



3. Digested with hydrochloric or with nitric acid, a part of it is also dis- 

 solved. 



4. The dissolved portion gave no trace of baryta, nor of strontia, nor of mag- 

 nesia, but a very slight one of lime, by the addition of oxalate of ammonia. The 

 presence of alumina was shewn by the addition of carbonate of ammonia to its 

 solution in nitric acid. Benzoate of ammonia, and ferro-prussiate of potassa, in 

 different portions of the neutralized solutions, indicated the presence of iron. 



After these preliminary experiments, I made the folio wing experiments in order 

 to find the relative proportions of its ingredients. 



B. 



From the difficulty of depriving a powder containing organic matter, wholly 

 of water, without partial decomposition, I was under the necessity of repeatedly 

 performing the process of desiccation and incineration. 



100 grains, gradually dried at a heat a little above 212, were introduced into 

 a platinum-crucible and heated to redness. The mass first blackened and gave 

 out the smell already noticed it was rather pungent ; and when litmus paper, 

 reddened by diluted acetic acid, was exposed to the vapour, its colour was imme- 

 diately restored ; and a rod dipt in hydrochloric acid, exposed to it, instantly pro- 

 duced white fumes ; shewing the evolution of ammonia. A full red heat, continued 

 for half an hour, converted it into a snow-white powder, which when weighed 

 before it was quite cold = 78 grains ; or the Berg-Meal by incineration had lost 22 

 per cent. The incineration was five times repeated on different quantities of the 



