Dr. Ure on Soda-Alum. 277 



oil of turpentine. It is 1.6 reduced to water, as unity. 110 

 parts of it are soluble in 100 of water at 60°; and form a 

 solution whose specific gravity is 1.296. In these respects, 

 potash-alum is very different; for I find that of this salt, from 

 eight to nine parts only are soluble in 100 of water at 60°, 

 yielding a saturated solution, the density of which is no more 

 than 1.0465. 



One hundred parts of soda-alum crystals lose by a heat 

 verging on redness 49, which seem to be merely water ; for the 

 residuary 51 parts re-dissolve in that liquid, without causing 

 any sensible cloudiness. By test solution of muriate of barytes, 

 I ascertained that 100 parts of soda-alum contain 34 parts of 

 sulphuric acid. The resulting muriates being evaporated to 

 dryness and ignited, weighed 23.3 of which 12.3 were found by 

 the action of water to be muriate of soda, and 1 1 alumina. 

 But 12.3 of muriate of soda are equivalent to 6.56 of that alkali. 

 To another 100 parts of this salt, I added water of am- 

 monia, in slightexcess, filtered, and exposed the well-washed 

 alumina to ignition, after which it weighed 10.5 parts. The 

 filtered liquid was evaporated to dryness and ignited. It 

 weighed 14.4 parts, and was dry sulphate of soda; for, on 

 re-dissolving it in water, and slowly evaporating the solution, 

 crystals in grooved six-sided prisms were obtained, amounting 

 to somewhat more than double the weight of the ignited salt ; 

 14.4 parts of dry sulphate of soda are equivalent to 6.4 soda. 

 From the mean of the above results, this soda-alum seems to 

 consist of 



Sulphuric acid, 34.00 



Alumina, 10.75 



Soda, 6.48 



Water of crystallization, 49.00 



100,23 

 Had leisure permitted me to repeat the analysis with greater 

 care, it is probable that the experimental quantities might have 

 come out more nearly as follows : 



