VOL. LXXXII.] PHILOSOPHICAL TRANSACTIONS. 225 



weighed 32.4 gr.; it had no taste or smell, but was an impalpably fine, intensely 

 black, and very light powder; for it occupied l-i- oz. measure, therefore may be 

 estimated to have been about 22 times lighter than water. A little of this black 

 powder, being thrown on a red-hot iron plate, ignited readily, but left a residue, 

 which was 4- of its weight: this being again thrown on the red-hot iron plate, it 

 ignited, and there remained, on cooling, a very small portion of brownish 

 powder, which diminished to almost nothing, by being applied twice more to the 

 iron kept red-hot for several minutes. On sprinkling this black powder on boil- 

 ing nitre, it sparkled most brilliantly and detonated, leaving a colourless mass 

 entirely soluble in water. This black powder, mixed with powdered nitre, defla- 

 grated on exposure to heat, in a retort with the air-apparatus affixed to it, afford- 

 ing, 'Over quicksilver, carbonic acid. This black matter also reduced the calx of 

 lead; being mixed with tartar of vitriol, and heat being applied, hepar sulphuris 

 was produced; and with phosphoric acid, phosphorus was obtained. That there- 

 fore these 32.4 gr. were charcoal, cannot I think be doubted. I might add, that 

 accidentally I found this powder, red-hot^ decomposed water as charcoal does. 



The above filtered liquid was evaporated to one pint, and showed signs of 

 acidity; to it was added muriated lime till it produced no further precipitation. 

 The dried precipitate weighed 1 30 gr., and was found to be phosphoric acid com- 

 bined with lime; and the liquor, in which this precipitation took place, was as- 

 certained to be muriated and acetated fossil alkali, with a little redundant acetous 

 acid, and a small portion of phosphoric selenite. 



The grey and white alkaline matter, with bits of melted glass, weighing 358 

 gr., as above-mentioned, by solution in concentrated acetous acid, afforded 4 1 

 oz. measures of carbonic acid, and a residue on the filter, which when well dried 

 weighed 44 gr. This residuum consisted of rough, sharp-pointed, black and 

 white particles; it was much specifically heavier than the residue of the other 

 part of the alkaline matter above-mentioned to have been examined; it defla- 

 grated a little on being thrown on boiling nitre, but left above 4 of its weight of 

 matter insoluble in water, and which I supposed was vitrified. The filtered liquor 

 from these 358 gr. of alkaline substance yielded to the precipitant muriated lime 

 21 gr. of phosphoric selenite. 



To satisfy myself still further, that carbonic acid had been destroyed in this 

 experiment, and to form some estimate of the quantity which had disappeared, 

 I separated it, by concentrated acetous acid, from 400 gr. of mild alkali, taken 

 from the same parcel as that which afibrded charcoal, and I found the quantity 

 to be 104 oz. measures, or 26 oz. measures in each 100 gr. of mild alkali. 



To afford a still more decisive proof that carbonic acid had not been combined, 

 or escaped, in this experiment, but had been destroyed, I exposed some of the 

 small parcel of alkali which had aftbrded charcoal to the same degree of heat, in 



VOL. XVII. G G 



