nSl'^iflicdidental s/^i^id^ Ittit art actiial augmentation of orti^ 



vbmrrie, a^ is proved by the potash alums, in which KO,SO^ 



has cidased to occupy space in solution, but on the crystallizai 



tion of the alum the volume becomes increased by One, ob^ 



viously owing to this peculiarity of KO, SO^ ; thus alum ift 



216 275 *• 



solution -^ = 24, becomes — = 25 in the state of a salt. ,.< 



This peculiarity is very striking, especially in the case 



KO^COIj, which with a volume, of ^r = 3 as a solidrber 



(ppp^p— = 1 as a hqmd. , liet us endeavour to conceive the 



extraordinary amount of power exerted in this case ; the wateir 

 in the volumenometer, on dissolving an equivalent of KO, C(\, 

 descends from 33 to 9, so that a bulk of solid matter = 24 grains 

 of water disappears Avithin it. If we would compare the force 

 to that which would be required to compress the water into 

 this diminished bulk, we must deal in numbers of a magni- 

 tude truly immense. We have always been accustomed to view 

 as an exception the expansion of water on becoming solid, but 

 now we see with Longchamp, that the rule is universal ; the 

 salt (muriate of ammonia excepted?) takes up more space as 

 a solid than it does in its liquid state in solution. . ,7 XZ.J 

 We have stated that we desire not to be held responsible for 

 any rash generalization of these laws, which we do not extend 

 at present beyond the salts examined by us. Let us con- 

 sider the volumes of the ammonia alums, as an example of 

 the danger of applying either of the laws without a proper 

 comprehension of them. These volumes are certainly above 

 275, the volumes of the potash alums, and are between 279 

 and 280, according to our experiments and those of Koppu 

 Now let us suppose that the four volumes of NH4O, SO3 are 

 represented in the alums, and that only AljOg, 3SO3 has 

 ceased to occupy space, as it in fact does when hydrated, 

 then an ammonia alum AlgOg, 3SO3 + NH4O, SO3 + 24HO 

 may be viewed as 9"8 x (24 + 4) = 279'4, an^^^the, specific 

 gravities would countenance this idea. !jp',^o^,f ovi^tl 



.« £i>loibc eiil i?£- g''- by Sp. gr. by our Bp. gr. by Kopp f 

 f , , Ineory. experiments. experiment, 



-f ^ASffiftoMrtifiSi^"'". 1-626 / 1-625 1-626 . 



Y*^^'- Ammonia iron alum 1726'^'^^'^"' I-7I8 1-71#^^'^ 



j These results certainly approach the theoretical number 

 veiy closely ; and the theory may represent the truth. Biit 

 at the same time it is difficult to believe that the ammonia 

 alum is constituted on a different type from the potash alum; 

 We might suppose that the only variation between them is the 



