IS 14. J Imperial Institute* S07 



But what renders it dangerous to examine this substance is, that 

 when it conies in contact with any combustible substance, as with 

 phosphorus, a violent detonation takes place, whieh breaks all the 

 vessels. This is a new example, and, as appears, the most energetic 

 of all, of those combinations in which the heat that kept the sub- 

 stances in the gaseous state still continues united with them, though 

 they have become liquid or solid; a case which chlorine presents 

 more frequently than any other body. M. Dulong proposed to 

 ascertain the proportions of the two constituents of this substance, 

 and its manner of acting on other bodies, especially on the metals ; 

 but the accidents which this young chemist met with at two diffe- 

 rent times, one of which deprived him of an eve, put an end to 

 his experiments ; and for the sake of the science, to which his 

 sagacity may still be of considerable service, the Class has engaged 

 him to turn his attention to other subjects. 



This same substance almost deprived chemistry of one of its 

 most illustrious cultivators, Sir Humphry Davy, formerly Secretary 

 of the Royal Society, who, though still young, has already made 

 numerous and brilliant discoveries, and particularly that" of the 

 metallization of the alkalies and earths, which opens a new field to 

 so many branches of the natural sciences. 



A substance not less remarkable has presented itself to M. 

 Cb'urtois, manufacturer of saltpetre at Paris. MM. Clement and 

 Desormes have shown it to the Class, and M. Gay-Lussac has made 

 upon it a set of instructive experiments. It is obtained from the 

 mother water of kelp by sulphuric acid and distillation. When 

 cooled and condensed, it has the appearance of plumbago. Before 

 it has been purified it melts at 158° ; but when purified by solution 

 in an excess of potash and distillation, it requires a much stronger 

 heat to melt it. Its most striking property is being converted by 

 heat into a violet coloured vapour, or gas, perfectly homogeneous 

 and transparent. Neither a red heat, nor oxygen, nor charcoal, 

 act upon it. It combines with the metals and their oxides, and 

 these combinations are soluble in water. With ammonia it produces 

 a fulminating powder. Sulphareted hydrogen discolours it, and 

 .cits it into a powerful acid; from which it may be again preci- 

 pitated by chlorine, sulphuric or nitric acid. In "fact iis action on 

 Other bodies is BO similar to that of chlorine, that it may be ex- 

 plained in a similar manner. We may either suppose it a peculiar 

 mbined with oxygen 5 or, with Davy, we may eonteeive it to 

 Ik- a simple substanee eatable of forming a peculiar acid by uniting 

 with hydrogi n. According to the Brat way or' viewing it, we must 

 suppose that the hydrogen unites with the superabundant oxygen, 

 and forms water, v\bieb cannot afterwards be separated From the 

 acid. What induced Davy to alter the received theory of oxymu.- 

 rhitic acid was, i| ): ,t hydrogen converts it into ordinary muiiatie 

 '. without its being possible t,, ,,1,,*;,, Bnv W ater. Yet water 

 ' have Lien formed if the hydrogen merely deprived the 



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