26 
DR. A. E. H. TUTTON ON THE 
and Rotter was never seen on ttiis salt, although the author has observed it on other 
salts of the series. 
In the next three tables the morphological constants of the three salts containing 
manganese are compared. From the first table it will be observed that the axial 
angle ft of the ammonium salt is fairly near to that of the csesium salt, and that the 
axial ratios of the ammonium and rubidium salts are also close to each other : the 
values for the ammonium salt clearly indicate the propriety of including this salt in 
this isomorphous series of double salts. 
The impossibility of preparing potassium manganese sulphate renders as complete a 
comparison as usual of the interfacial angles of a group impossible ; but the angles of 
the ammonium salt are very obviously related to those of the rubidium and csesium 
salts in a manner similar to that which has been observed in the other groups 
investigated, where the complete set of four salts has been obtained. Like the axial 
ratios, the angles indicate clearly that the ammonium salt does belong to the same 
series as the rubidium and csesium salts. 
Cleavage .—There is an excellent cleavage parallel to the orthopinakoid r'{201}, 
and also a fairly good cleavage parallel to the clinopinakoid b {010,. 
Comparison of the Axial Angles and Axial Katios. 
Axial angle. 
Axial ratios. 
ft. 
a : h : c 
Rubidium manganese sulphate . 
105° 57' 
0-7382 : 1 :0-4950 
Ammonium ,, „ 
106° 51' 
0-7400 : 1 :0-4931 
Csesium ,, ,, 
107° 7' 
0-7274 : 1 :0-4913 
Comparison of the Interfacial Angles. 
Angle. 
RbMn sulphate. 
CsMn sulphate. 
Am Mn sulphate. 
ac = (100) : (001) 
o / 
74 3 
o / 
72 53 
o / 
73 9 
as = (100) : (101) 
45 27 
44 37 
45 1 
sc = (101) : (001) 
28 36 
28 16 
28 8 
< 
cr = (001) : (201) 
63 58 
64 55 
64 19 
cs = (001) : (101) 
38 23 
38 48 
38 20 
s'r = (101) : (201) 
25 35 
26 7 
25 59 
r'a = (201) : (100) 
41 59 
42 12 
42 32 
[ap =(100): (110) 
35 20 
34 51 
35 18 
J 
pp =(110): (120) 
19 28 
19 28 
19 28 
1 
p'b = (120) : (010) 
35 12 
35 41 
35 14 
L pb = (1 ]0 ) : ( 010 ) 
54 40 
55 9 
54 42 
jcq =(001): (Oil) 
25 30 
25 11 
25 16 
\qb =(011): (010) 
64 30 
64 49 
64 44 
