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ROYAL SOCIETY OF CANADA 



the pycnometer was 2.44. The result of the analysis is given in the 

 following table: — 



In the last column are the numbers calculated for AljOa.NaaO. 

 2C02.2HjO. 



Although lime was present, its percentage is very much lower than 

 in the other analyses of Montreal dawsonite. A second analysis 

 gave 3.75^ CaO. It is interesting to note that the carbon dioxide is a 

 little high, and almost exactly by just such an amount as would com- 

 bine with the whole of the lime to form carbonate. Disregarding this 

 as a foreign admixture, thé recalculated analysis agrees very closely 

 ■with the theoretical figures (see last two columns in table). This would 

 seem to confirm Dr. Harrington's opinion that the lime found in analyses 

 of Canadian specimens is present as admixed calcite; and also, to show 

 that in all probability there is no isomorphous replacement of Nag by Ca, 

 even partially, in dawsonite, ])ut that the latter is entirely foreign to the 

 composition of the crystals. 



In looking over the literature of the subject, I find that various 

 formuliE have been given to dawsonite by different authors, and in some 

 cases they are not in agreement, as the following will show: — 



1. Al,0,Na,0.2CO.,.2H.,0 = NaAlCH^O^] p^jg^g, 



2. Al2{CO,Na)5(OH)« = NaAlCH, OJ 



3. Na, TAl,] C.,0„ . 2H,0 = Na Al C H, O^ — Harrington. 



4. 3Na,C0,.Al,(C0s)3.2Al,(0H)g. ... = Na Al CH, O, — Am. J. Sc. Ill, 22.157 



5. NarAl(0H),l.C0,. =NaAlCH,0,l Dana's System. 



6. ''Na,Al(C03),.2AHOn), =NaAlCH,0,J 



7. NaAl(0H)C0, = Na Al C H 0, ( ^^l^^^^n^^J " ^ ^ * ' 



