m the Isle Wight, 243 



Sulphats contained in a pint of the Water. 



Sulph, of baryt. 

 ignited. 



Sulphat of iron (§ VIII. 9) 41,4 grs. crystallized = 31,8 grs.* 



Sulphat of alumina (§ IX. 5) 3,8 grs. ignited alumine = 17,7 ditto f 



Sulphat of lime (§ X. 4) 10,17 grs. dried at 160° = 13,9 ditto t 



Sulphat of magnesia (§XII. 2) 3,63 grs. crystallized = 4,0 ditto || 



Sulphat of soda (§ XIV. 7) 16,0 grs. crystallized =11,6 ditto § 



Total amount of the sulphat of barytes 79,0 grs. 



* These proportions were deduced from the following experiment : 50 grains of crys- 

 tallized green sulphat of iron were dissolved in water, and nitrat of barytes was added 

 as long as any precipitate took place. The sulphat of barytes after being carefully 

 edulcorated and heated to redness in a platina crucible, weighed 38,5 grs. Therefore 

 50 : 38,5 :: 41,4 : 31. 



+ It may be recollected that 3,8 grs. of ignited alumine, would, according to the 

 proportion before stated (§ IX. 5,) correspond to 31,6 of crystallized alum. I found 

 by a direct experiment that 100 grs. of regular octohedral crystals of alum formed by 

 gradual deposition from a saturated solution of common alum, being dissolved in water 

 and precipitated by muriat of barytes, produced 88,2 grs. of Ignited sulphat of barytes ; 

 so that the 31,6 grs. of alum would correspond to 27,8 grs. of the barytic sulphat. 

 This, however, could not be an accurate estimate of the real quantity of sulphuric acid, 

 since the sulphat of alumine does not exist in the v.ater in the state of alum. 



With a view to learn the proportions of acid and ha.se in pure sulphat of alumine, I 

 Bnade the following attempt. A quantity of alumine (which had been prepared by pre- 

 cipitation from alum, redissolution in muriatic acid, and second precipitation by car- 

 bonat of ammonia, and appeared to contain no impurity except a vestige of muriatic 

 acid), was dissolved in sulphuric acid, and the solution evaporated to siccity. When re- 

 duced to tV.e consistence of a thick syrup, and allowed to cool, the saline mass congealed 

 into a hard whitish deliquescent cake, capable of being pulverized. This was redis- 

 solved and re-evaporated four successive times, and the last time was made red-hot, ia 

 rder to expel the excess of sulphuric acid which always appeared to prevail. By this 

 last operation a portion of the salt was decomposed and rendered insoluble in water, 

 in spite of which the remainder still exhibited signs of acidity. The clear solution of 

 this mass being divided into two equal portions, one of which was precipitated by suc- 

 cinat of ammonia, and the other by nitrat of barytesj yielded 4,6 grs. of ignited alumine, 



2 H 2 



