148 



arseniates, have not been produced as such, directly ; but that in the first 

 instance compound phosphates or arseniates have formed. Magnesia and 

 ammonia, singly or collectively, being the other members of the term. The 

 magnesia and ammonia being afterwards gradually substituted by the metallic 

 oxide. A continued supply of such metallic oxide to the compound phosphate 

 or arseniate, would almost certainly effect this, the metallic phosphates and 

 arseniates being more insoluble than the alkaline ones. 



2nd. This property of some of the metallic phosphates, etc., of combining 

 with phosphate of magnesia and ammonia, to form insoluble compounds, makes 

 it very probable that several of these natural phosphates and arseniates may 

 contain very appreciable quantities of ammonia or magnesia. At any rate, I 

 think, with this property manifested, it would be well to examine rigorously 

 this class of compounds, for either of these substances. 



These notes are, of course, merely preliminary, there being several points 

 of interest left undiscussed, which can only be properly represented along with 

 the results of future investigations. 



Art. XXVIII. — On the effects of the Application of the Hot Blast to Blow- 

 pipe-purposes: and the proposed substitution of Heated Air for Oxygen in 

 the production of certain thermal and illuminating effects. Preliminary 

 notice. By W. Skey, Analyst to the Geological Survey of New 

 Zealand. 



[Read before the Wellington Philosophical Society, June 19, 1869.] 



The useful and well-known effects of the hot blast, in the process of iron 

 smelting, has induced me to try and extend it profitably to other purposes, 

 beyond that which prompted its application in the present instance. 



My experiments, as yet, have been confined to testing the effects of 

 substituting a hot blast, for a cold one, as hitherto used, for the production of 

 the well-known blowpipe flame ; a flame so produced will be expected to have 

 its thermal and illuminating effects augmented, but scarcely, perhaps, to that 

 degree which experiment has demonstrated. 



I had better state, at the outset, those particulars which it is necessary 

 to know, before relating the results. 



The temperature of the blast was, approximately, 500° F., the diameter of 

 the jet, regulating its issue, was one-thirtieth of an inch, the combustible for 

 receiving the blast was stearine. 



This flame manifested a very marked superioi'ity over the common 

 blowpipe flame, — substances difficult to fuse in the latter, magnitite, potash- 

 felspar, mica, readily yielded under these circumstances ; while thick glass 

 tubes half an inch in diameter, and hard G-erman glass tvibes, were tractable to 

 an eminent degree. 



Carrying my test experiments still further, I found several substances, 

 for the fusion of which the oxy-hydrogen flame, or some equivalent of it in 

 heating power, is said to be indisjjensable, also yielded before the blowpipe 

 flame thus urged : for instance, platinum, pipe clay, fire clay, agate, opal, 

 flint. 



Several samples of each were tried and always with the same results, it 

 could not well be, therefore, that the fusibility of any of these substances was 

 due to the accidental presence of foreign matter, in more than usual quantity. 



The platinum was the common platinum foil, also a sample prepared 

 especially for the purpose ; the only impurity found in it was iron, as traces, 

 communicated to it in the act of forging : possibly minute quantities of some 



