MONO CLINIC DOUBLE SULPHATES CONTAINING AMMONIUM. 
metals. The first series (on the left) shows the ratios when the /3-axis of each 
salt is taken as 1, and the second (right hand) series when the /3-axis of the potassium 
salt is taken = I ; this second series thus shows the effect on the optical ellipsoid of 
replacing one alkali base by another. In both series the position of' the ammonium 
salt is between the rubidium and ciesium salts, and much nearer to the former. 
Molecular Optical Constants .—These have been calculated with the aid of the 
densities as determined by the immersion method, both for the ammonium salt now 
under discussion, and for the potassium, rubidium, and caesium salts, and the results 
are set forth comparatively in the next three tables. 
The specific refraction and dispersion of ammonium nickel sulphate are considerably 
higher than those of the alkali-metal salts. The molecular dispersion is slightly higher 
than that of the caesium salt. The molecular refraction, whether calculated by the 
formula of Lorenz, or by that of Gladstone and Dale, is very close to (just higher 
than) that for the rubidium salt. The mean molecular refraction shows this very 
succinctly. 
Table of Specific Refraction and Dispersion (Lorenz). 
Sulphate. 
n 2 _ i 
Specific refraction, —--- = n. 
1 (n 2 + 2) d 
Specific disper 
“ Ho- 
sion. 
For ray C (Ha)- 
For ray Hy near G. 
cl. 
A 
7- 
cl. 
A 
y- 
cl. 
A 
y- 
AmNi . . . 
KNi .... 
RbNi . . . 
CsNi . . . 
0-1509 
0-1273 
0-1113 
0-1035 
0-1524 
0-1290 
0-1125 
0-1042 
0-1543 
0-1321 
0-1143 
0-1048 
0-1545 
0-1300 
0-1137 
0-1057 
0-1561 
0-1318 
0-1149 
0-1064 
0-1580 
0-1349 
0-1167 
0-1070 
0-0036 
0-0027 
0-0024 
0-0022 
0-0037 
0-0028 
0-0024 
0-0022 
0 • 0037 
0-0028 
0-0024 
0-0022 
Table of Molecular Refraction and Dispersion (Lorenz). 
Salt. 
Molecular refractio 
7l 2 - 1 
M 
1 “ m ' 
Molecular dispersion. 
m G - m c . 
o c\ * 
At" -f- 2i 
For ray C (Ha). 
For ray Hy near G. 
CL. 
A 
7- 
CL. 
A 
y- 
CL. 
A 
y- 
KNi sulphate 
55-23 
56-00 
57-31 
56-41 
57-20 
58-53 
1-18 
1-20 
1-22 
RbNi 
58-53 
59-19 
60-10 
59-79 
60-46 
61-40 
1-26 
1-27 
1-30 
AmNi ,, 
59-17 
59-77 
60-49 
60-58 
61-22 
61-95 
1-41 
1-45 
1-46 
CsNi 
64-20 
64-61 
64-97 
65 • 55 
66-00 
66-34 
1-35 
1-39 
1-37 
