224 PHILOSOPHICAL TRANSACTIONS. [aNNO 1792. 



the affinity is not so strong between carbonic acid and fixed alkalis, as between 

 carbonic acid and quick-lime, and because the mechanical separation of charcoal 

 from alkalis, and phosphoi-ated alkalis, may be more easily made than of char- 

 coal from calcareous earth and phosphoric selenite. The purest fossil alkali I 

 could ];rocure was employed, from which I had expelled -j^ of its weight of 

 water, but none of its carbonic acid. 



Into a thick white glass tube, almost 1 incli wide, 34- feet in length, coated 

 within 9 or 10 inches of the open end, were introduced 200 gr. of transparent 

 phosphorus, and 800 gr. of the above deaquated alkali were pressed down on 

 them. The tube, thus charged, was then bent so that the open end might be 

 kept conveniently plunged in quicksilver during the experiment. The coated 

 part of tiie tube, containing the alkali, excepting 2 or 3 inches next the phos- 

 phorus, was gradually heated over a portable furnace till it was red-hot, and 

 rather flexible, in which state the part containing the phosphorus was gradually 

 drawn over the fire, and kept red-hot 20"'. At the beginning of the experiment, 

 quicksilver rose several inches within the tube, and when the coated part became 

 hot, phosphorus was sublimed into the upper and cool part of it: about 20 drops 

 of water were condensed over the quicksilver; and 2 oz. measures of phlogisti- 

 cated air, with a little respirable air, which had the smell of phosphorus, came 

 over. The tube, when cold, being broken, the lower part was found to contain 

 a loosely-cohering solid, as black as charcoal, which weighed 428 gr., and above 

 this, a grey and white substance, partly fused, and partly in a powdery form, 

 which, with adhering glass, weighed 358 gr. Neither in this, nor in other si- 

 milar experiments, was I able to collect the whole contents of the tube, without 

 glass which had been melted, that adhered to the alkali, on which account I 

 could not determine accurately the total weight, independently of glass; but I 

 was sure, from a number of trials, that it was a little less than the original weight 

 of the alkali. The phosphorus, sublimed into the upper part of the tube, was 

 moist from the adhering phosphoric acid: it was inflamed by slight friction, viz. 

 merely on breaking the tube. 



The 428 gr. of black alkaline matter thus obtained, afforded, by solution in 

 boiling hot concentrated acetous acid, a little more than 25 oz. measures of car- 

 bonic acid, under the mean pressure of the atmosphere, and ot the temperature 

 of 4 5°; that is, 100 gr. of the black matter yielded about 6 oz. measures of this 

 elastic fluid. In other Mmilar experiments, the quantity of carbonic acid varied 

 from 4 to 7 oz. measures in 100 gr. of this blackened alkali; except in 1 expe- 

 rinient, which afforded only 3 oz. measures of the acid, but the largest propor- 

 tion of charcoal I ever niade, namely, 12 gr. 



The solution of the above 4'i8 gr. was filtered, and the residue, which was 

 black, was lixiviated with boiling distilled water. Tliis residue when dried, 



