- 206 T. S. Hunt on the Constitution 
| Species, | Formula. Equiv. wt. | Density, Volume. 
Phosphate soda, |POsNa2H, 24HO 399° 1 1525 | 235°5 
Sub-phos. soda, |POsNas,24HO 3816 PQ22.. | 2352 
Arseniate soda, jAsOsNa2H,24HO 402°9 1:736 {| 233-0 
Sub-arsen. soda, |AsOsNas,24HO 425°2 | 1-804 | 235°6 
The four species of alum examined by these experimenters ex- 
hibit a similar relation. They are monometric in crystallization, 
and, like the last, are represented with 24HO, common alum be- 
ing SsalsK Ore, 24HO; the al may be replaced by fe or er, 
lents given by Playfair and Joule have been corrected from later 
determinations of chromium and aluminum. 
Formula, Equiv. wt. Density. Volume. 
Saals KOie, 24HO 474-6 1-731 2741 
Saals (NH4)016,24HO 453°4 1-625 279°0 
S4acrs KOi16,24HO 500°6 1:843 2716 
Safes (NH1)O16,24HO 482:0 1-715 280°5 
The densities here adopted are the means of those of several 
experimenters. Playfair and Joule, from different specimens of the 
same species, obtained results, some of which we cite to show the 
amount of variation in crystals of a pure salt. "Thus, for potash 
alum the numbers 1:726 and 1-751 were obtained, giving respec- 
tively 275 and 271 for the volume; and for chrome alum, the 
densities 1826 and 1-856, corresponding to 274-15 and 268°6. 
For reasons already given, the presumption in these salts is in fa- 
vor of the greater density, adopting which, we have for the mean 
of the four species 274°6, and for the first three, 272°8, as the 
equivalent volume. 
_ The monometric species leucite is represented by the formula 
K; Sig+3Al Sin, which expanded becomes SisO2,, (aloKs) O12 
with an equivalent of 665-22 and a density of 2-49, giving 267 
for the volume. The triclinic species andesine, belonging to the 
same type, has an equivalent of 622-2 and a density of 2:7, giving 
230-4 for its volume. This difference of volume in these an 
other dimorphous species has already been pointed out by Dana. 
If we turn from the alums and leucite, to the chlorids of potas- 
sium and sodium, which likewise crystallize in the regular sys- 
tem, we find at first sight no apparent relation with the former, 
or between each other. The one NaCl, with an equivalent 
weight of 59-4, has a density of 2-257, which gives 26°3 for its 
volume, while the chlorid of potassium K Cl, with an equivalent 
of 74-5, has a density of only 1-978, (P. and Joule,) giving a vol- 
ume of 37-67. If we suppose crystallized sea salt to be 10Na Cl, 
we shall have 263: for its volume, and the potassium salt may be 
7KCl, with a volume of 265-7. We are thus Jed to the conclu- 
xperiments 
sion arrived at by Favre and Silbermann, from their e 
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