150 



loss, surely sufficient if properly economised ; but as I have already shown, 

 this excess of temperature can be largely increased. 



In view of the greater controllability of the proposed substitute, — the 

 absence of all clanger in its use — its not requiring chemical preparation, — and 

 its cheapness, compared with oxygen ; upon these several points, respectively, the 

 question should be properly tested. 



Besides the substitution of oxygen urged above, the possible fusion of the 

 purer clays, and certain silicas, etc., in a ready and economical manner, may 

 induce the further utilization of these substances, while in experimental 

 chemistry the facility with which such high temperatures can be attained and 

 kept up, may lead among other things, to some cheaper way of extracting 

 certain metals from their oxides, aluminium, for instance, from alumina or clay. 



On reviewing these results, it does seem not a little singular that a 

 difference of not more than 500° F., in the temperature of the blast, should 

 make the difference between the fusibility and infusibility, of such substances 

 as platina, agate, fire clay, etc., in the blowpipe flame. It will be recollected, 

 however, that the blast has, in this case, not only taken up the heat required 

 to raise a single volume of it to this temperature, but another portion of heat 

 has been taken up in a latent form, as the air expanded, — consumed as it were 

 in lifting against the atmospheric pressure ; this may be represented suffi- 

 ciently well for us, by assuming the temperature of the blast, kept to its 

 normal volume, at 700° F. 



This is as yet, however, but a very slight addition to produce resrdts, 

 which so nearly approximate to those obtainable by the oxy-hydrogen flame, 

 seeing the latter has an estimated temperature of 14,000° to 15,000° F., while 

 that of the present method does not much exceed 5,000° F. The gap, as far 

 as effects is concerned, is narrowed so much, and in a manner so unexpected, 

 by the results here given, that one is naturally prompted to enquire whether 

 the assigned temperature of the oxy-hydrogen flame has been obtained by 

 direct experiment, or by calculations, based upon the ascertained temperature 

 of other flames. The temperature as calculated, indirectly, in this last way, 

 certainly furnishes us with figures remarkably close to those just quoted. 



In reference to this impoi*tant point I beg to call attention to a notice, 

 which appeared in the " Chemical News," relative to the imperfect combustion 

 of certain gases at high temperatures. 



There we learn that at moderately high temperatures (much below 

 10,000° F.) oxygen and hydrogen only very partially combine, — from memory, 

 I believe, not more than to the extent of half their weight, — the remainder of 

 the gases of course combine, as the centre of heat is left behind. Thus, 

 although the quantity of heat evolved by their combustion is the same, being 

 divided over a larger volume, its intensity is proportionately diminished. 



This being so, it would seem to follow, that the temperature of the oxy- 

 hydrogen flame must be very considerably lower than that hitherto ascribed to 

 it ; and therefore the possibility of substituting it in this, or in some other 

 manner equally economical, for the several purposes here specified, appears so 

 much the greater. 



Art. XXIX. — On the alkalinity of Carbonate of Lime. By W. Skey, 

 Analyst to the Geological Survey of New Zealand. 

 [Read before the Wellington Philosophical Society, July 17, 1869.] 

 Carbonate of Lime is described, in chemical works, as neutral to test paper, 

 but this scarcely agreeing with the insults of observations I have had to make 

 upon this point, in the course of other investigations, I beg to give these 

 res\ilts, which are as follows : — 



