48d FMILOSOPHICAL TRANSACTIONS. [aNNO 17 67. 



From the foregoing experiments it appears, that 1 lb. of the spirit of salt 

 vapour, condensed in the water in experiment 2, is to I lb. of the acid of salt, 

 which dropped into c of the same experiment, as 200 is to lOQ, which is nearly 

 double; and therefore the 61b. 12 oz. and -l of the vapour, which condensed 

 in the water, is equal very nearly to 13 lb. 1 oz. of the acid which is distilled in 

 c : so that by this method of distillation, this great proportion of acid is saved, 

 and those disagreeable suffocating fumes avoided. 



In experiment 3, lib. of the acid vapours, which condensed in the water, is 

 to lib. of the acid of salt which dropped into c, as 131 is to 50, or as 244 to 1 ; 

 and therefore the 3 lb. 10 oz. of acid vapours, which condensed in the water is 

 almost equal to 9 lb. and -^ of what distilled into c. 



It further appears, that the slower the distillation is conducted, the more 

 concentrated are the acid vapours that condense in water. In order to see 

 whether there was any difference in the strength of the acid vapours, which 

 were condensed in the water from the first to the last of the distillation, the 

 following experiments were made. 



Five pound of common salt, with 5 lb. of oil of vitriol, were distilled in a 

 tubulated retort; and 3 bottles, with an equal quantity of water in each, were 

 made use of to condense the vapours. The first bottle increased in weight 3 oz. 

 and during this time, which was 12 hours, there was no fire under the retort; 

 that bottle being taken away, another bottle put under, a fire was made: this 

 bottle increased in weight 1 lb. and half an ounce, the third bottle increased 

 10 oz. and a half. 



As much water of each of the 3 bottles, as contained one ounce and a half 

 of the acid fumes, was saturated with an alkali dissolved in water. 



The water of the 1st bottle took to be saturated II oz. 4^ a dram. The 2d 

 bottle took up 10 oz. 2 dr. 2 scr. The 3d bottle 10 oz. 1 dr. An ounce and 

 half of oil of vitriol, which was to 'water, as 226 to 1 18 nearly, took up of the 

 same alkali 7 oz. 6 dr. 



By which it appears that the fumes, which first arose without fire, are stronger 

 than the second, and the 2d than the 3d. It appears further, that the most 

 concentrated portion of the acid of sea salt is the most volatile, and that in 

 strength it is to the oil of vitriol mentioned before, as 44^ to 3 1 . 



* In order to try the purity of the acid vapours, which were condensed 

 in the water, and of the acid which distilled into the bottle c, the following 

 experiments were made, and are marked a, b, c, d. 



* This depends on the property of the acid of vitriol, and the acid of sea salt, combined with a 

 calcarious earth; for this earth, corabined with the acid of sea salt, forms a very soluble substance; 

 whereas the same earth, with the acid of vitriol, forms a substance insoluble, or almost so, called 

 selenite.— rOrig. 



