VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. 5 



saturate a given quantity of fixed alkali, exactly the same as that of marine acid 

 whose quantity I determined ; and to prove the truth of this supposition, I ob 

 served the specific gravity of the spirit of nitre and oil of vitriol I made use of, 

 and in which I supposed, from the trial with alkalis, a certain proportion of acid 

 and water ; to these I then added more acid and water, and calculated what their 

 specific gravities should be on the above supposition ; and finding the result to 

 accord with the supposition, I concluded the latter to be exact. 



The experiments made on the marine acid were as follow : I took 2 bottles, 

 which I filled nearly to the top with distilled water, of which they contained in 

 all 1399.9 gr. and introduced them successively into 2 cylinders filled with ma- 

 rine air, which I had obtained from common salt by means of diluted oil of 

 vitriol and heat, in a mercurial apparatus; and this process I renewed till the 

 water had imbibed, in 18 days, about 794 cubic inches of the marine air. The 

 thermometer did not rise all this time above 55°, nor sink, unless perhaps at 

 night, under 50°, and the barometer was between 29 and 30 inches. This 

 water, or rather spirit of salt, I then found to weigh 1920 gr. that is 520.1 

 more than before. The quantity of marine air absorbed amounted then to 

 520.3 °t. I then examined the specific gravity of this spirit of salt, and found 

 it to be 1.225. Its loss of weight in water (that is, the weight of an equal bulk 

 of water) should then be 1567.346 gr. nearly ; but it contained only, as we have 

 seen, 1399-9 gr. of water : therefore, subtracting this from 1567.346, the re- 

 mainder (that is, 167.446) must be the loss of 520.1 gr. of marine acid; and 



consequently the specific gravity of the pure marine acid, in such a condensed 



520 1 

 state as it is in when united to water, must be [ fi ' . = .3100. But still it might 



be suspected, that the density of this spirit did not entirely proceed from the 

 mere density of the marine acid, but in part also from the attraction of this acid 

 to water, and though the length of time requisite to make water imbibe this 

 quantity of acid made me judge that the attraction was not very considerable, 

 yet the following experiment was more satisfactory. 



I exposed 1440 gr. of this spirit to marine air for 5 days, the thermometer 

 being at 50° or under ; it then weighed 1562 gr. and consequently imbibed 122 

 gr. of marine air; its specific gravity was then 1.253, which agrees exactly with 

 what it should be by calculation Being now satisfied I had discovered the pro- 

 portion of acid and water in spirit of salt, I was impatient to find it in other 

 acids also ; and for that purpose I took 180 gr. of very strong oil of tartar per 

 deliquium, but of whose specific gravity I can find no note, and found it to be 

 saturated by 180 gr. of spirit of salt, whose specific gravity was 1.225. Now, 

 by calculation it appears, that 180 gr. of this spirit contains 48.7 gr. of acid, 

 and 131.3 of water; and hence I drew up the following table. 



