MR. J. B. HANNAY ON THE MICRORHEOMETER, 
283 
time at first it saves confusion, hence I use the above arrangement. It will be seen 
from the above table that each metal and metalloid or acid radicle has a value of its 
own, because it does not matter which way the compounds be written, the result is 
the same; whether we take KN0 3 +NaCl or K01+NaN0 3 , we get a retardation of 
4'3". Thus on mixing the solutions we get as an average of 10 experiments— 
Salts. 
Time. 
Difference. 
Probable error of mean. 
KNOg + NaCl 
133-45 
+ 2-15 
0-08 
KOl + NaNOg 
133-45 
+ 2-15 
o-io 
Water 
131-3 
or as the solutions by being mixed are diluted to half strength, on doubling the value 
we get 4’3" as before calculated. A series of solutions were then made up and their 
values determined. The following table gives the results, the numbers given being 
the average of 10 experiments. The time was determined by a stop-watch which beat 
fifths of seconds, and I found, after having conducted over 500 experiments, that my 
personal error was reduced from 0'6 of a second to 0’3, that being the general average 
of the greater bulk of the work. Each number is the mean of 10 experiments. 
Salts. 
Time. 
Probable error of mean. 
Difference. 
Water 
13P3 
// 
0 
Potassic nitrate 
126-4 
0-06 
— 4-9 
,, chloride 
129-0 
0-08 
- 2-3 
,, bromide 
126-4 
0-15 
- 4-9 
,, iodide 
123-9 
o-io 
— 7-4 
,, sulphate 
143-6 
0-25 
+ 12-3 
Sodic nitrate 
137-9 
o-io 
+ 6-6 
„ chloride 
140-7 
0-14 
+ 9-4 
,, iodide 
135-7 
0-06 
+ 4-1 
,, sulphate 
155-3 
o-io 
+ 24-0 
Ammonic nitrate 
125-5 
0-08 
- 5-8 
,, chloride 
128-1 
0-14 
- 3-2 
„ sulphate 
142-5 
0-12 
+ 11-2 
Magnesic nitrate 
155-0 
0-12 
+ 23-7 
,, chloride 
157-3 
0-26 
+ 26-0 
,, sulphate 
171-9 
0-30 
+ 40-6 
Baric nitrate 
141-4 
0-14 
+ 10-1 
„ chloride 
144-0 
0-15 
+ 12-7 
Strontic nitrate 
143-2 
o-oo 
+ 11-9 
,, chloride 
145-8 
0-07 
+ 14-5 
Calcic nitrate 
145-0 
o-io 
+ 13-7 
„ chloride 
147-6 
0-05 
+ 16-3 
,, sulphate 
152-2 
1-48 
+ 30-9 
Cupric nitrate 
150-2 
0-12 
+ 18-9 
,, chloride 
152-9 
o-oo 
+ 21-6 
,, sulphate 
167-4 
0-20 
+ 36-1 
2 O 
2 
