Dr Thomson's Chemical Analysis of an Indian Mesolite. 187 



resemblance to the rocks at Dumbarton, from which so many 

 beautiful zeolites have recently been extracted. It may be fre- 

 quently observed in these islands, detached from its native rock, 

 among the debris with which the sides of the high lands are 

 always profusely supplied. This mineral has hitherto been 

 procured in considerable abundance in Scotland and Germany, 

 find specimens from each of these situations differ slightly in 

 their composition. It is from this circumstance, that the pre- 

 sent analysis is now submitted to the reader, as I find that the 

 Indian variety is characterised by an additional quarter atom 

 of water, a fact which will be more distinctly perceived in the 

 formulae. 



The Indian specimen resembles the mesolites of Scotland in 

 its mineralogical characters, but has a lower density. Its specific 

 gravity, by a mean of two trials, is 2.262. Before the blow- 

 pipe per se curls up ; fuses with borax into a colourless bead 

 with difficulty. Ten grains reduced to a fine powder were 

 boiled with some pure muriatic acid, to which a little nitric acid 

 was added; by this means the powder was converted into a 

 jelly. Distilled water was now poured upon it, and the whole 

 solution evaporated to dryness. Very dilute acid being then 

 added to the dried powder, by digestion the silica alone remained 

 undissolved, Avhich was thrown on a filter and well washed. 

 When dried, heated, and weighed, it amounted to 4.27 grains. 

 Before the blowpipe, with carbonate of soda, this product fused 

 into a colourless glass, shewing that it consisted of pure silica. 

 The liquid which passed through the filtre was concentrated, 

 and caustic ammonia was added. The alumina, which fell in 

 fine white flocks, was thrown on a filter and washed with warm 

 distilled water. The precipitate, after being dried and heated 

 to redness, weighed 2.75 grains, which dissolved completely 

 when boiled in muriatic acid, demonstrating that no silica ex- 

 isted mixed with it. Caustic potash, when boiled with the so- 

 lution left no precipitate, shewing that no iron was present in 

 the mineral. The washings of the alumina were concentrated 

 on the sand-bath, and the solution rendered neutral. A solution 

 of oxalate of ammonia produced a copious white precipitate, 

 which was thrown on a filter. The carbonate of lime produced 

 1.36 grains, which is equivalent to .761 lime. The remaining 



