486 PHILOSOPHICAL TBANSACTIONS. [aNNO 176?. 



Next morning, all being cold, another gallon of water was added as before, and 

 a very slow fire made under the body for 14 hours, in which time there distilled 

 near a pound of volatile alkali ; the fire was then made stronger, and continued 

 in that state for 12 hours more, in which time there was obtained, together with 

 what was first distilled, S^lb. of volatile alkali, strong and fit for eau de luce; 

 this was taken out of the bottle and set apart. The vessels being cool, 2 gallons 

 more of water were put into the body, and the fire made as before, and conti- 

 nued till there was 7 lb. distilled of weak volatile spirit ; this answers better than 

 water for a fresh distillation of sal ammoniac and lime. 



During the first 1 6 hours of the distillation, there continually escaped through 

 the water of f elastic air very slightly charged with volatile alkali, especially 

 when the water got hot; but during the remaining time of the distillation, no 

 elastic air was set free. 



Two stone gallon bottles, with 3 quarts of water in each, were made use 

 of to condense the vapours; and when one bottle was got warm by the fumes, 

 the other was put in its place, while it was cooling in a vessel of cold water; 

 and so continually changed during the whole operation. The 6 quarts of water 

 increased by this means 2\h. and -^ in weight; and, by the following experiments 

 it appears, that a pound of this vapour condensed in the water, is to a pound of 

 the volatile alkali, which was set apart for Eau de luce, as 140 to 76, which 

 is nearly twice as long; therefore there was a saving of near 5lb. of volatile 

 alkali, which would have been lost in the common manner of distillation. 



The water of the two stone bottles charged with alkaline vapours was mixed, 

 in order to reduce them to the same degree of strength, and as much of it was 

 put into a glass cucurbit, as contained 4 ounces of the alkaline vapour; 4 

 ounces of the volatile alkali, which was set apart for Eau de luce was put into 

 another cucurbit of the same size, and diluted with water to the same volume 

 of the other. 



This last took lib. 3oz. of acid of vitriol, diluted with water, to be saturated, 

 and did not become hot; whereas the water containing the 4 oz. of the same 

 add of vitriol, and got so very hot, that the vessel could scarcely be held in the 

 hand, even after having been diluted at different times with 2 quarts of water. 

 This shows that there is a great difference in the two, and that it is not entirely 

 owing to strength. The heat produced by the vapours passing through the 

 water, was tried at another distillation, and raised the quicksilver in Fahrenheit's 

 thermometer to 110 degrees. 



In rectifying caustic volatile alkali with lime, there is likewise a very great 

 quantity of elastic air set free, highly charged with volatile alkali, which 

 condenses in water and heats it. Water may be so strongly charged with this 



