VOL. LXXKII.] PHILOSOPHICAL TRANSACTIONS. "24/ 



all the substances found in this earth, which have been tried, gravitate equally. 

 This additional matter must be added to the metal either from the acid, the 

 alkali, the water used in the solution, the air lying on the surface of the mate- 

 rials during the time of the operation, or it must come through the vessels in 

 which the operation is performed. To ascertain this, I made the following 

 experiment. 



I took a large quantity of vitriolic acid, purified by distillation, (about 1 lb., 

 it not being material what quantity was taken exactly) ; I diluted it with 

 distilled water, about 4 or 5 times its weight by guess (the exact proportion 

 beinf also immaterial); I applied to 1000 grs. of this diluted acid a sufficient 

 quantity for saturation of aqua kali puri, of the Lond. Disp., rendered pure 

 from fixed air, as is prescribed in the process of the college ; I poured in the 

 aqua kali puri to the diluted acid, by a little at a time, till it was nearly saturated ; 

 I then poured in some juice of violets, which gave the whole a red colour. I 

 continued to add aqua kali puri, by a little at a time, till the red colour just 

 disappeared. I added the aqua kali puri to the acid, rather than the acid to the 

 alkali, because the loss of the red colour at the point of saturation can be dis- 

 cerned much better than the loss of the yellow colour, which the alkali inter- 

 mixes with the natural blue. 



I ascertained the weight of the aqua kali puri, by weighing the bottle contain- 

 ing it before any was poured into the acid, and after the saturation took place ; 

 the deficiency of weight afterwards being the weight of the aqua kali puri applied 

 to the acid for the saturation ; this was 10147 grs. I also weighed the vessel 

 with the acid before the aqua kali puri was poured in, and afterwards ; and found 

 the increase of weight to be exactly the same as the weight of the aqua kali 

 puri and juice of violets, so that nothing was lost during the operation. This 

 experiment was 3 times repeated, taking the point of saturation from the eye. 

 The quantities of aqua kali puri employed were found to be 10147 grs., 10145 

 grs., 101 50 grs. 



I took 10148 grs., being the mean of the 3 experiments, and applied it to 

 1000 grs. of the same vitriolic acid ; evaporated the water to dryness, and heated 

 it to a red heat, to drive off the whole of the water ; and found 978 grs. of kali 

 vitriolatum remaining. By this means I ascertained the quantity of kali vitriolatutn 

 produced from 1000 grs. of the diluted vitriolic acid, when saturated with kali. 



I took 1000 grs. of the diluted vitriolic acid, and put it into a vessel, of the 

 form in fig. 8, pi. 2, I added zinc to it till it would dissolve no more ; I caught, 

 during the solution, the inflammable air, which weighed g grs., and whose 

 specific gravity was, to atmospheric air, as somewhat less than 1 to 12. The 

 %'essel contained the whole of the acid and the zinc in the globular part marked 

 A, the acid being introduced by a funnel. The solution was terminated in 5 days,; 



