Atomic Volume and Specific Gravity. 



519 



hnc if: 



-.•a 



The important researches of Graham have shown that water -,, 

 plays a most important part in the constitution of salts ; and 

 that salts with an excess of base may be viewed as hydrates, 



in which oxide of hydrogen becomes replaced by a metallic 



oxide. The previous experiments will be found to give this 

 theory the fullest confirmation. Sulphate of zinc crystallizes™ — 

 with seven atoms of water and affects a volume of 74*6 ; and 

 sulphate of copper assumes the same state of hydration, when 

 crystallized with the latter salt, although per se it assumes 

 only five atoms. Placing together the subsulphates and hy- 

 drated sulphates of these metals, we perceive not only a close 

 similarity in their formulae but also in their volumes, as ascer- 



S80C isr^jjjgj ]jy experiment. 



ZnO, SO3, 3HO, 4HO, vol. 

 ZnO, SO3, 3ZnO, 4HO, .. 



CuO, SO3, 3HO, 4HO, vol. 

 CuO,S03,3CuO,4HO, .. 



•0.1 



74-6 \ I 

 76-2/' 



74 



7Q 



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... (iiis^iH lo sindqluioiozl 



^ii-.ji;iffi io sJisriqIoewl 



y-fr'ff'iffT '^o MiBiiqluadoB 



... X'-Q- iijiji io oiKOTOidD 



' ; . :-<iidodisB 



The difference between the two states of the sulphates iS(jmdu8 

 probably greater as stated than it actually is. We have al- i"8 ,A 

 ready shown that the magnesian sulphates with seven atoms 

 of water do not possess a volume of 77'0, because two of the'^^*!*^"^ 

 atoms possess a volume of 9*8 instead of iro ; and perhaps''^-*- -^ 

 a similar circumstance tends to reduce the volume of the sub-;'j^?''^g 

 sulphates. Similar instances of replacement of water by a ,qqoo 

 metallic oxide are seen in other parts of the table. We have '^"'^'(^ 

 already shown that nitrates of copper and bismuth possess 4 nmn/ 

 volume of 58"8 or 9*8 x 6. We have also seen instances 

 in which 9'8, the volume of ice, in feeble compounds, be-' 

 came changed into the volume 1 1 when the salt entered into'|°|^^^ 

 combination. In this point of view, the subsalts MO, NOgnomffiA 

 + HO + 2MO become assimilated to the hydrated nitrates jommA 

 MO, NO5+ HO + 2HO, the number of volumes in both;-,o(j3 

 cases being the same, the only difference being, that, in thctornmA 

 former case, the salts are multiples of 11, and in the latter™^ 3 

 of 9'8, or the volume of ice. The hydrated type affects six "[^^^^yg 

 volumes, and so do the subnitrates, as will be. s^enby the r(i;,iiig 

 following table. , ^,t, i f V> ^f-wB hue ')tv:uhoJj> 



CuO, NO5, HO + 2CuO, volume 65-9 or 11x6 ^ , 



BiO,N05, HO + 2BiO, ... 66-0 ,,,11x6 

 HgO, NO5, HO + 2HgO ... 65-6 j^.^'lrj^e ^''"*^'''^ ^'f ^ 



We have further evidence of the equivalency of water to the 



metallic oxide in anhydrous nitrate of bismuth, which has a 

 volume of 55*0 or 66— 11 ; the formula for the salt being 

 BiO, NO5+ 2BiO. The conversion of the volume 9-8 into 11 



