Mr. H. C. Sorby on Jargonium. 69 



The alteration produced in jargons by heat is, to some slight 

 extent, analogous to what occurs on heating carbonate of lime in 

 the state of arragonite ; but, instead of changing into an opaque 

 mass of minute crystals of another form of the carbonate (calcite, 

 which has a less specific gravity, is less hard, and does not give a 

 different spectrum), they are still as simple and transparent crystals 

 as at first, the specific gravity and hardness are increased, and the 

 spectrum is entirely changed. Iodide of mercury is an excellent 

 illustration of an alteration in the spectrum, due to a change in 

 crystalline form produced by heat ; but still the facts differ most 

 materially from those described, and there are only two modifications 

 — the yellow and the scarlet. The existence of three crystalline 

 modifications is similar to what occurs in titanic acid. Anatase, 

 Brookite, and rutile have distinct crystalline forms ; but they do not 

 differ much in specific gravity, and their spectra present no charac- 

 teristic differences. On the whole, the different states of carbon 

 (charcoal, graphite, and diamond) are perhaps the best illustration 

 of the existence of three different conditions in the same substance, 

 since they differ materially in specific gravity and optical characters, 

 one being black, the other having a metallic lustre, and the third 

 being transparent and colourless ; but these are variations of the ele- 

 ment itself, and not, as in the case of jargonium, modifications of its 

 compounds. So far as I am aware, there is indeed no substance which 

 shows strictly comparable facts. 



There cannot, then, I think, be any doubt whatever that jargo- 

 nium is not only a new elementary substance, but is also one likely 

 to throw much light on several important physical questions. By the 

 time that the Society resumes its meetings, I trust that I shall be 

 able to send a complete account of the whole of my investigations, 

 including such facts connected with other substances as may serve to 

 illustrate the very peculiar properties of this hitherto unrecognized 

 element. 



Postscript. 



I here subjoin a brief account of the methods employed by Mr. 

 David Forbes* and myself in separating zirconia and jargonia from 

 one another. He separated apparently pure zirconia by means of 

 strong hydrochloric acid, which dissolved the chloride of jargonium, 

 but left chloride of zirconium undissolved; and obtained the ap- 

 proximately pure jargonia by adding to the solution excess of am- 

 monia, and then considerable excess of tartaric acid, which left most 

 of the tartrate of jargonia insoluble, but dissolved what may turn 

 out to be a mixture of zirconia and jargonia with a third substance, 

 not yet sufficiently studied — perhaps Svanberg's noria. My own 

 analysis was only qualitative. I fused powdered jargon with several 

 times its weight of borax, which gave a perfectly clear glass, com- 

 pletely soluble in dilute hydrochloric acid. After separating the 



* Chemical News, June 11, 1869, vol. xix. p. 277. 



