VOL. LVII.3 PHILOSOPHICAL TRANSACTIONS. 395 



small quantity of volatile alkali ; as it left 4 grs. of a brownish salt, which being 

 re-dissolved in water, yielded a smell of volatile alkali on the addition of lime. 

 It is doubtless this volatile alkali which is the cause of the precipitate, which the 

 distilled water makes with sugar of lead and corrosive sublimate. What first 

 suggested to Mr. C. that the distilled water contained a volatile alkali, was the 

 distilling some of it over again in a retort; by which the first runnings were so 

 much impregnated with volatile alkali, as to turn paper, died with the juice of 

 blue flowers, to a green colour, and in some measure to yield a smell of volatile 

 alkali. 



In the foregoing experiment, the salt procured from the distilled water was 

 perfectly neutral; so that the quantity of acid employed was certainly not more 

 than sufficient to saturate the alkali, but it may very likely have been less ; as in 

 that case the superfluous volatile alkali would have flown off in the evaporation. 

 The following experiment shows pretty nearly the quantity of volatile alkali in 

 the distilled water. 



Exper. 2. 1128 oz. of Rathbone-place water were distilled in the same manner 

 as the former. The distilled water was divided into 2 parcels, that parcel which 

 came over first weighing 121 oz., the other 146. A preparatory experiment 

 was first made, in order to form a judgment of the comparative strength of each 

 parcel, and also of the quantity of acid which it would require to saturate them. 

 This was done by dropping sugar of lead into each parcel till it ceased to make a 

 precipitate. It was judged from hence that the first parcel contained about 2-J- 

 times as much volatile alkali as an equal quantity of the second. Into 30 oz. of 

 the first parcel, mixed with as much of the second, was then put 43 grs. of oil 

 of vitriol, which was supposed to be about \ more than sufficient to saturate the 

 alkali in it. The mixture was then evaporated. When reduced to a small quan- 

 tity, it was found to be rather acid : 16 grs. of volatile sal ammoniac were there- 

 fore added, which seemed nearly sufficient to neutralize it. Being then evapo- 

 rated to dryness, it left 66 grs. of a brownish salt, which dissolved readily in 

 water, leaving only a trifling quantity of brown sediment. A little of this salt 

 was found to make no precipitate on the addition of fixed alkali, and the re- 

 mainder, being boiled with lime, was converted into selenite; a sure sign that 

 the salt was merely vitriolic ammoniacal salt. The volatile alkaline salt con- 

 tained in Q() grs. of vitriolic ammoniacal salt, is 58| grs. ; from which deducting 

 1 6 grs., the weight of the volatile sal ammoniac added, it appears that the dis- 

 tilled water used in this experiment, contains 42-j- grs. of volatile salt ; and 

 therefore the whole quantity of volatile salt driven over by distillation, seems to 

 be about 68 grs., which, as the 2d parcel was so much weaker than the first, is 

 probably nearly the whole volatile alkali contained in the water. 



Exper. 3. Dr. Brownrig, in a pajx;r printed in the Phil. Trans, for 1765, 



3 E 2 



