of Edinburgh^ Session 1880-81. 197 
Table VI. 
Temperature, 
° c. 
28 
47 
70 
Permanganate used . 
• 
15-95 
11-9 
3-8 
Chlorate used, per cent. 
• 
9-2 
33-5 
77-1 
The effect of dilution on the rate of action will be apparent from 
Table VII. Tor each experiment 10 c.c. of ferrous sulphate (a) were 
allowed to react on 10 c.c. chlorate of potash along with 10 c.c. H 2 S0 4 , 
and different quantities of water, which will be apparent from the 
figures giving the total volume of the solution. After standing 
exactly half an hour they were titrated with permanganate. In 
the last four experiments in this table the sulphuric acid used was 
formed by diluting 1 part of oil of vitriol with 4 parts of water 
(both by weight) ; it may therefore be written 2H 2 S0 4 , as there are 
two gramme-molecules in the litre. Three blank experiments gave 
17 ’6 as the permanganate equivalent to the 10 c.c. ferrous sulphate. 
Table VII. 
Temperature, . 0 C. 
18 
17 
16-7 
12-8 
12-7 
12-7 
12-8 
Volume of solution, c.c. 
40 
80 
120 
30 
60 
90 
120 
Permanganate used, ,, 
10-95 
15-35 
16-4 
9-2 
14-5 
16-15 
16-8 
Chlorate used, per cent. , 
37-7 
12-7 
6*8 
47-8 
17-8 
8-5 
4-8 
I hope shortly to be in possession of more extensive experimental 
data, and to discuss them in a future paper. 
7. On some Space-Loci. By Professor Tait. 
{Abstract.) 
The class of problems treated is one to which considerable atten- 
tion has been paid of late, as for instance by Glaisher and others in 
this country, and by Mannheim, &c., abroad. 
Two years ago (Proc. 1879, p. 200), in connection with Minding’s 
Theorem, I investigated the space-locus of the feet of perpendiculars 
from the origin on the rays of a complex. These were found to fill 
the space bounded by the two sheets of the reciprocal of a Tresnel’s 
wave-surface. The method I employed is capable of very extended 
