508 
PROFESSORS A. W. REINOLD AND A. W. RDCKER ON THE 
increased. The following Table (Table III.), exhibits the results obtained. We follow 
the plan which we have adopted in previous papers of calculating the percentage of 
KNO 3 reference to the soap solution only. Thus, if equal volumes of the two 
liquids were compared, a 10 per cent, liquide glyceriqiie would contain the same 
amount of KNO 3 as a 6 per cent, solution of soap in water only, the proportion of 
salt to soap being the same in each case. 
Table III.— Liquide Ghjceriqiie ; 1 part of soap to 40 of water in all cases. 
Date. 
Percentage of 
KNO 3 . 
Thickness in yu./t., measured 
optically. 
Mean. 
1891 
8-66 
8-.3, 9-7, 9-4, 10-5 
9-5 
95 
0-2 
/107, 11-0, 10-6 1 
111 - 8 , 11 - 2 , 11 - 2 / 
11-1 
188.3 
30 
flO- 6 , 10-2, 12-5, 10-71 
110-2, 11-0, 9-4 / 
10-7 
1891 
0-0 
23-9, 2.y4 
• 
24-7 
These figures are, we think, sufficient to prove the truth of the proposition. 
We now 23 ass from a study of the effect of a change in the proportion of salt to 
that of an alteration in the quantity of soap dissolved, the optical method of 
measuring the thickness being still adhered to. 
O O 
Proposition III.—If the p>roportion of oleate of soda in a solution containing no 
p)Otassium nitrate he diminished, the thickness of the film, as measured by the optical 
method, increases. 
Table IV.—Hard Soap. No dissolved Salt. 
Proportion of 
soap to water. 
Thickness of black film in /t.a., 
measured optically. 
Mean. 
1 to 30 
21-8, 21-7, 21-0, 22-0 
1 
21-6 
1 „ 40 
23-2, 22-3, 20-3, 22-8 
22-1 
1 „ 60 
28-1, 27-4, 27-6 
27-7 
1 „ 80 
28-8, 29-4, 29-8 
29-3 
The first point to notice is that the results given in this Table strengthen the 
argument in favour of Proposition II. One part of soap was used with 50 of water 
in the two solutions first referred to in Table I., but in the case of the last two the 
proportion was 1 to 40. The above Table proves that, had the proportion of soap 
been the same in all cases, the relative thickness of the films formed with a solution 
containing no KNO 3 would have been even greater than appears from Table 1. It is, 
