412 Mr. Brayley, Jiin., on the Existence of' Salts of Potash 



mon with all other chemists, lie now enjoys, he could scarcely 

 have tailed to detect the presence of sulphate of potash in the 

 varieties of salt, &c., he examined, supposing them to have con- 

 tained it. But since his estimates of the constitution of sul- 

 phate of barytes and oxalate of lime, from which his deduc- 

 tions were made, are both slightly in error, it cannot be satis- 

 factorily determined, from the merely general statements given 

 in his paper, whether he would have detected an excess of 

 sulphuric acid or not, by the processes and estimates he ac- 

 tually em]:)loj'ed. It seems most probable, however, especially if 

 the quantity were minute, that he would not have detected an 

 excess of this kind. For example : the Lymington salt, as may 

 be seen by recomputing Dr. Henry's results, might have con- 

 tained 1*2 16 parts in 1000 of sulphate of potash without his 

 detecting it* ; and since the sulphate of potash of sea-salt must 

 be one of those saline combinations which are chiefly left in 

 the mother-liquor, we should not expect Lymington salt to 

 retain more than a minute quantity, like this, of sulphate of 

 potash, out of the proportion oi'iginally existing in the sea- 

 water from which it is manufactured. 



This reasoning extends to all Dr. Henry's aucdyses; not 

 only of the rock-salt and the varieties prepared from the 

 Cheshire brine, but also of the varieties of sea-salt, and of the 

 bitterns, as well from brine as from sea-water, and of the im- 

 pure kinds separated from both fluids during the crystallization 

 of the muriate of soda. If the varieties of salt he examined 

 contained muriate of potash, it must be included in what Dr. 

 Henry regards, by estimation, as "pure muriate of soda." 



But Mr. Horner, in his analysis of the Droitvvich brine f, in 

 which he found chloride of sodium, sulphate of lime, and 

 chloride of magnesium, found also an excess of sulphuric acid, 



* Dr. Henry obtained from 1000 grains of Lymington salt " ;51 grains 

 of calcined sulphates, consisting of" 19 grains of dry [anhydrons] suliiliate 

 of magnesia, and V2 grains of dry [anhydrous] suljihate of lime." " Now 

 from the magnesian sulphate," he continues, " 38 grains of sulphate of 

 barytes should residt, and from the sulphate of lime 21 grains, the sum of 

 which is 59. But the quantity actually obtained was .i9'H. Tiiere is only, 

 therefore, an excess of 08 grain of the actual above the estimated quan- 

 tity ; a difference much too trivial to be admittetl as an indication of any 

 sulphate with an alkaline base : and arising probably from unavoidable 

 errors in the experiment." — Phil. Trans. 1810, p. 115; or Phil. Mag. vol. 

 xxxvi. p. 17*>- 



Rccoinputation of these results: as GO : 118 : : 19 : 37".'360; and as 

 68:118:: 12:20-823. The sum of these corrected results is 58-189 

 grains, which subtracted from 59-8 leaves l-G.'il as the excess of the 

 actual above the estimated quantity of sulphate of barytes. Now as 

 118:88:1-631:1-210, which, therefore, is the proportion of sulphate of 

 potash in the Lymington salt tiiat might have escaped detection. 



t Trans, of Geol. Soc. Ist series vol. ii. 



which 



