The Chemistry Of Common Things.

aquafortis . It is very caustic , and corrodes and dissolves nearly all " the metals , and is extensively employed in etching on copjier , and in many of the arts and manufactures . Thus it appears that the tAA'o gases of AA'hich our atmosphere is composed form by their combination a class of bodies differing veidely from one another in all their qualities and properties . When they

are merely mechanically mixed , as in the atmosphere , they constitute a gas eminently fitted for the support of life and combustion , totally devoid of taste or smell , colorless , incapable of being reduced to tho liquid or solid state b y any degree of cold or pressure that has yet been applied . When chemically combined in a certain proportion , they constitute a gas Avhich has « sweet tastean agreeable odourand

, , produces intoxicating effects by inhalation . When another -proportion of oxygen is added , a gas in produced possessing none of the qualities of the former , but destructive to life , and incapable of supporting combustion . Acid two more proportions of oxygen , and a gas is obtained of a brilliant red color . Avith acid qualities , none of the other compounds exhibiting —> rhen pure—any trace of colouring .

Lastly , add another proportion *> i oxygen , and Ave have one of the most poAverful and corrosive acida knoAvn . Their constitution also furnishes us with a striking example of the principles -of equivalents , or combining proportions of bodies . The composition of the compounds is as folloAvs : —

By Aveight . By volume . Nitrous oxide r : If nit . -f lox ., or 2 nit . -f lox . Nitric oxide = If nit , -j- 2 ox ., or 2 nit . -j- 2 ox . Nitrous acid = If nit . - { - 4 ox ., or 2 nit . + 4 ox . Nitric acid = If nit . + 5 ox ,, or 2 nit . - \ - Sox . From Avhich it appears that the quantities of oxygen combined in

each case Avith one' and three quarters part by wei g ht , or two parts by volume of nitrogen , are as the numbers , 1 , 2 , 4 , and 5 . If Ave attempt to combine fractional parts of oxygen with the ono and three quarters part of nitrogen wo shall find that the gases will combine iu such proportions as to form one of the four compounds , and the residue of either gas AA'ill remain free . Hence it appears that nitrogen Avill

combine with oxygen only whore they arc in the proportion of one and three quarter parts of the former to an integral number of parts of the latter , One and three quarters is therefore said to be the equivalent atomic Avei ght or combining proportion of nitrogen , that of oxygen being one . It Avill be seen that there is a gap between the nitric oiicle and the

nitrous acid , the proportion of oxygen contained in the four compounds being respectively I , 2 , -1-, and 5 . To render the series complete , there should be a compound wliich contains three equivalents of oxygen , united with one of nitrogen . This place is actually filled by the hyponitrous acid , an acid Avhich has never yet been obtained iu a separate state , but has been found in connection with alkaline bases , forming salts called hyponitrites or pernitrites ;