BY W. F. PETTERD, C.M.Z.S. 



189 



101-16 



This has to be explained as follows: — The insoluble por- 

 tion was that part not affected by acids. The soluble 

 portion was extracted by treatment with aqua regia, but 

 as the ' solubles ' and " insolubles ' did not aad up 130 per 

 cent, a special test was made by subjecting the stuff to a 

 fairly high heat. In this treatment, not alone whatever 

 water may have been present there was driven out, but 

 doubtless also a certain portion of fluorine, and, as it may 

 have been present, some hydroxyl, which is now considered 

 to be present in topaz. For this reason the determination 

 of the ' solubles ' is probably slightly incorrect. Neverthe- 

 less, the errors do not affect the general acceptation of 

 the material as topaz. It is only a moot point whether 

 the soluble alumina is to be added to the insoluble alu- 

 mina or not. As far as concerns the calcium fluorite, 

 which was found in the soluble portion, this may be 

 regarded as being extraneous matter, but it is uncertain 

 how much fluorine may be included in the ignition loss. 

 The insoluble portion analysed for itself gives the follow- 

 ina* results: — 



The analysis as a whole may therefore be arranged as 

 follows, allowing a small discrepancy in the fluorine : — 



104-87 



