Although the substance called Natrolite by Mr. Klaproth has lately been found, under a crystalline form, perfectly similar to that of mesotype, M. Haily has not thought himself warranted, from this circumstance, to consider these two bodies as of the same species, on account of the difference of their chemical composition; because, according to the analysis of M. Vanquelin, there was not observed to be any soda in zeolite,,but, on the contrary, a considerable quantity of lime, which is not a constituent part of natrolite.
Mr. Smithson, on the contrary, is inclined to consider them as the same substance, by the agreement of their chemical properties, as well as crystallographical form. Although he had, many years since, found that the zeolite of Stajfa contained soda, as has since been observed by Dr. Hutton and Dr. Kennedy, he still felt uncertain whether these were of the same kind as those analysed by M. Vauquelin: but having lately received from M. Hafiy a cluster of mesotype in rectangular prisms, terminated by a quadrangular pyramid, Mr. Smithson took this opportunity of ascertaining whether this substance and natrolite did or did not differ in their composition. The method pursued by the author in the analysis of zeolite was first to expose ten. grains of it to a strong heat, for the purpose of ascertaining the loss; and he found it to be '95 grain. An equal quantity was then dissolved in muriatic acid; and after the solution been evaporated to dryness, the residuum was exposed to a red heat. Water was then poured upon it, and dissolved a portion, which, upon evaporation, was found to be muriate of soda, weighing 3‘15 grains. From the solution of this salt, neither carbonate of ammonia nor oxalic acid occasioned any precipitate; by which it appeared that this zeolite contained no lime.
The residuum from which the muriate of soda had been extracted was next digested in muriatic acid, which dissolved a part. but left undissolved a quantity of silica, which, after being made red hot, weighed 4'9 grains. The muriatic solution was then evaporated to dryness, and exposed to a red heat; and the residuum appeared to be pure alumina. Since it was possible that some magnesia might also be mixed with it, it was dissolved in sulphuric acid, and ignited; but the residuum was not found to yield any sulphate of magnesia by addition of water to it. The whole of the sulphuric acid, however, had not been expelled by heat, but was afterwards separated by nitrate of barytes; and the alumina was estimated to amount to 2.7 grains.
The results thus obtained accorded so nearly with the analysis of natrolite, as given by Klaproth, that it was judged unnecessary to repeat his experiments on that substance.
Mr. Smithson is induced to prefer the name of Natrolite to that of Mesotype, from a desire to preserve unaltered the name given by Baron Cronstadt, the original discoverer of this class of bodies; and
