M. Scheerer's Observations on Elaolith and Nepheline. 113 



II. QUANTITIES OP HYDROCHLORIC AND SULPHURIC ACID IN 

 ELJEOLITHS. 



In the preceding analyses I have omitted two constituents 

 which well deserve a separate consideration : these are small 

 quantities of hydrochloric and sulphuric acids which occur in 

 these minerals. M. Bromeis first drew attention to this sub- 

 ject, and I have fully confirmed his observations. To test 

 the various species of elaeolith as to the quantities of these 

 acids, I always employed distinct quantities, which, powdered 

 finely, were decomposed by chemically pure nitric acid. The 

 muriatic acid was then determined by a solution of silver, and 

 the sulphuric acid by chloride of barium. M. Bromeis found 

 in the white elaeolith from the Ilmen mountains 0'04? per 

 cent, hydrochloric acid. I obtained the following results: 



Hydrochloric Sulphuric 

 acid. acid. 



Green elaeolith from Arendahl ' . . trace trace 2 exp. 

 Brown elaeolith from the same loO 



cality . j trace 



White elaeolith from the Ilmen 1 __ ^ 



mountains J 



Nepheline from Monte Somma . . 0-22 O'lO 1 exp. 

 The same 0'05 trace 2 exp. 



The first and second experiment with the nepheline differ 

 very much, which probably arises from a quantity of those 

 crystals being taken which were employed for the analyses 

 10 and 11, containing foreign minerals which, as for instance 

 davyne, might easily increase the amount of the acids. As the 

 quantities are so small, I will not vouch for perfect accu- 

 racy in the quantities stated'* 1 ; thus much is, however, cer- 

 tain, that they exist in the elaeoliths examined. They are 

 not expelled by exposing the mineral to a red heat, but may- 

 be detected in the mass after heating, which is as easily de- 

 composed by acids as before. Nor can they be extracted from 

 the finely powdered mineral by boiling in water; it hence re- 

 sults that they cannot be simply combined with an earth or an 

 alkali, but form an essential mineral combination, probably 

 replacing a small quantity of silica. At first I suspected that 

 the portion of silica, always remaining undissolved on decom- 

 posing the mineral with nitric acid, might possibly produce 

 opacity with a solution of silver; but this cannot be the 

 case, as the opacity, with different species of elaeolith, under 

 similar circumstances, differed considerably ; thus, for in- 



* Especially as the small quantities of the chloride of silver were always 

 of a blackish colour, and not fusible. 



Phil. Mag. S. 3. Vol. 17. No. 108, Aug. 1840. I 



