Atomic Volume and Specific Gravity. 



487 



ceding section we observed tliat sulphate of potash possessed 

 the singular property of expanding one vohinie in becoming 

 solid; 9 X 2 in a state of solution becoming 11.x 3 in the 

 state of a salt. It is impossible to refrain from accepting this 

 as an explanation of the increase of one in the quotient ob- 

 tained by dividing tlie volumes by their proper numbers, Q 

 and 11 — 24 x 9 becoming 25 x 11. 



The difficulties, to which we have already alluded, prevent 

 us placing much confidence in our results for the anhydrous 

 alums. Sulphate of alumina seems to affect eight volumes of 

 ice, 9*8 X 8 = 1B>'^\ in ammonia alum the latter becomes 

 united to the volume of anhydrous sulphate of ammonia, 

 9'8 X 8 + 9'8 X 4 = 117*6; while potash alum should con- 

 sist of 9*8 X 8 + 11 X 3 = lir4. It is unnecessary to re- 

 mark that these theoretical numbers possess only an approx- 

 imation to our experimental results. [Vide remarks on Sec- 



tion V. 



.rf.im'Oi:! 



vtisdqlUfi 



The sulphates of soda and silver' ^nd the corresponding 

 chromate are also obviously exceptions to the general rule of 

 the solid volume being multiples of 11. But in the last section 

 we had similar exceptions in salts which ranged themselves 

 under 9*8 or the volume of ice. The sulphates now under 

 consideration have the same divisor, if sulphate of soda be not 

 considered an exception, as the variation is decidedly too great 

 to be attributed to a mere error of experiment ; it ought how- 

 ever to be observed that Mohs gives for the specific gravity 

 of this salt 2*462, a number much more in accordance with 

 theory than our own result ; but as our experiments have been 

 often repeated, they may perhaps be viewed as an argument in 

 favour of an opinion, deduced from other considerations, that 

 sulphate of soda has a double atom 27*5 x 2 = 55, which 

 is 11 X 5. 



Name. 



V 2 



Sulphate of soda '27-5 3 



Sulphate of silver ' 29-4 3 



Chromate of silver 29-2, 3 





29-4 

 29-4 

 29-4 



2 ^ 



2-430 

 5-322 

 5711 



2-597 

 5-322 

 5-770 



lu n&9» 



Section III. 



Nitrates f ^c. 



The nitrates do not in general aflect a large proportion of 

 water of hydration, and are therefore well-calculated to show 



