VOL. LVII.] PHILOSOPHICAL TRANSACTIONS. 487 



vapour, that it will make very strong Eau de luce, nay, much stronger than that 

 which we said before was distilled and set apart for Eau de luce; but it is 

 necessary, as mentioned before, to make use of 2 stone bottles, changing them 

 as often as they get warm. ■ •^^' *-^ 



Exper. 2. — On the distillation of the acid of salt by means of the acid of 

 vitriol; see the apparatus fig. 2. * A green quart retort, coated with loam, was 

 made use of for this experiment, and it was placed in a reverberatory furnace on 

 a naked fire; 14lb of common salt was put into it, and on that the like 

 quantity of oil of vitriol, which had been diluted the day before with 7lb. of 

 water; the retort was then immediately luted to the recipient, and the distilla- 

 tion conducted in the common manner: the operation continued 1 6 hours, 

 when hardly any more liquor would come over with a strong fire. To con- 

 dense the vapours, 2 stone gallon bottles, with 3 quarts of water in each, were 

 made use of, as in the former experiment. 



In this operation there was obtained gib. 5oz. and 4- of spirit of salt, which 

 dropped into the bottle c; the 6 quarts of water in the stone bottles increased 

 in weight 61b. 12 oz. and 4; the caput mortuum weighed 18lb. 6 oz.; so that in 

 this operation there was only a loss of 8 oz. which is but y^ part of the whole, 

 which probably was mostly elastic air. 



Exper, 3. — The same operation was repeated with a slower fire, which 

 continued for 23 hours, after which time hardly any more liquor would come 

 over with a strong fire. There were here produced 11 lb. 10 oz. of spirit of 

 salt, in the bottle c; the 6 quarts of water increased in weight 3lb. 10 oz. and 

 the caput mortuum weighed IQlb. 4 oz.; the loss was the same as in the fore- 

 going experiment. 



In order to know the different degrees of strength of the acids produced in 

 these two experiments, they were saturated with a fixed alkali, dissolved in water. 

 Four ounces of the acid in experiment 2, which distilled into c, took of the 

 alkaline liquor to be saturated 13 oz. 5 dr. 2 scr. As much of the water 

 -f- in experiment 2, as contained 4 oz. of vapour, took to be saturated 1 lb. Q oz. 

 Four ounces of the acid in experiment 3, which dropped into c, took of the 

 same alkaline liquor to be saturated, 12 oz. ^. As much of the water of 

 experiment 3, as contained 4 oz. of vapour :{;, took to be saturated, 2 lb. 6 oz. 

 Four ounces of oil of vitriol, which was to water in weight as 24 to 13, took 

 of the same alkaline liquor to saturate it lib. lOoz. 7 dr.; which shows that 

 oil of vitriol is not so strong an acid as the vapour of spirit of salt, when con- 

 densed in water and distilled slowly, as in experiments. 



• What goes by the name of a quart retort, holds better than 2 gallons of water. — Grig. 



+ The water of the 2 bottles was mixed together; for they were of different strength. — Orig. 



t The water of these 2 bottles were likewise mixed together for the same reason. — Orig. 



