Page:Popular Science Monthly Volume 58.djvu/135

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HEN the chemists of olden times had reduced a body to oil, salt, earth and water, they believed that they had reached the limits of chemical analysis, and consequently they gave to salt and to oil the names of 'principles of bodies.'

In proportion as the art made progress, the chemists who succeeded them became aware that substances which had been held to be primary could be decomposed, and they recognized in succession that all the neutral salts, for instance, were formed by the union of two substances, an acid of some sort and a salt, earth or metal.

Hence arose the entire theory of neutral salts which has held the attention of chemists for over a century, and which is to-day so near perfection that we may regard it as the surest and most complete part of chemistry.

Chemical science has been handed down to us in this condition, and it is our business to do with the constituents of the neutral salts what the chemists who went before us did with the neutral salts themselves, to attack the acids and bases and to carry chemical analysis along this line a step beyond its present limits.

I have already imparted to the Academy my first efforts in this field. I have in earlier memoirs demonstrated to you as far as it is possible to demonstrate in physics and chemistry that the purest air, that to which M. Priestley has given the name of 'dephlogisticated air,' enters as a constituent part into the composition of several acids, notably of phosphoric, vitriolic and nitric acids.

More numerous experiments put me in a position to-day to draw general conclusions from these results and to assert that the purest air, the air most suitable for respiration, is the principle which causes acidity; that this principle is common to all acids, and that in addition one or more other principles enter into the composition of each acid, differentiating it and making it one sort of acid rather than another.

In consequence of these facts, which I already regard as very firmly established, I shall henceforth call dephlogisticated air or air most suitable for respiration, when it is in a state of combination or fixity, by the name of 'the acidifying principle,' or, if one prefers the same meaning in a word from the Greek, 'the principle Oxygine.' This nomenclature will save periphrases, will make my statements more exact, and will avoid the ambiguities I would be likely to fall into constantly if I used the word 'air.'