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XXI. Analysis of Caporcianite and Phakolite, two nerc Minerals of the Zeolite 

 Family. By THOMAS ANDERSON, M.D. Communicated by Dr CHRIS- 



TI80N. 



(Read, April 18. 1842). 



THE minerals of the zeolite family have for many years attracted the espe- 

 cial attention of men of science, and the class has been rapidly extended in pro- 

 portion to the progress made in its study in a crystallographic as well as chemical 

 point of view. The first characteristic difference, originally observed long since 

 by CRONSTEDT, and by him considered to be the distinguishing mark of one single 

 mineral species, which he designated Zeolite, namely, the property of swelling 

 out by heat previous to fusion, has since been found to belong to a great 

 number of other combinations. These, although materially different from each 

 other in crystallographic form, have proved to be closely allied in chemical con- 

 stitution, in so far as they consist, without exception, of a silicate of an alkali 

 or alkaline earth, in combination with a silicate of alumina and water. It is 

 evident, then, that the relation of the silicic acid to the base, in both terms, as 

 well as the quantity of water, is capable of considerable variation, so that the ge- 

 neral mineralogical formula which should embrace all the members of the zeolite 

 family would be 



u r S" + x A Sy + A q. 



Where r represents the monatomic alkaline or earthy basis, and the terms u, v, x, 

 y, and z, are capable of varying within certain limits. 



The minerals Caporcianite and Phakolite form two new members of the above 

 general formula. Their analysis was conducted in the following manner : 



The finely pulverized mineral was dried for several days over sulphuric 

 acid in an exsiccator, at the ordinary temperature of the atmosphere. A certain 

 quantity of the dry powder was then weighed in a small tube retort, and heated 

 to moderate redness for the space of half an hour. The water thus driven off was 

 absorbed in a counterpoised tube of chloride of calcium and weighed. Another 

 portion of the dry powder was then dissolved in hydrochloric acid, and evapo- 

 rated to dryness for the separation of the silicic acid. The dry mass was then mois- 

 tened with hydrochloric acid, digested for several hours, and dissolved in water, 

 and the silicic acid filtered off. The purity of the silicic acid was then tested by 

 solution in a boiling solution of carbonate of soda ; the undissolved matter, which 

 VOL. xv. PART u. 4 u 



