500 PROFESSOR HENRY A. MIERS : AN ENQUIRY INTO 
the total reflection method can be relied upon, and that there is no sudden break in 
the curve. 
In this particular series there is a considerable dislocation of the curve between 
Nos. 10 and 11, due partly to the fact that the corner of the rectangular trough used 
in this experiment interfered with the illumination, and partly that, for fear of 
causing the liquid to crystallise, it was not efficiently stirred until this point was 
reached. For this reason the series is not plotted on Diagram I. 
Table II. represents a series of isolated oliservations made by the method of total 
reflection upon saturated solutions at the ordinary temperature. In Nos. 1 to 4, 
which relate to the same solution, the temperature was not recorded; but the effect 
of approximation to crystals in the solution is here traced; No. 1 is a saturated 
solution ; in No. 2 a few small crystals have been placed in the trough; in No. 3 a 
mounted crystal is liroiight near to the prism ; in No. 4 it is brought almost into 
contact with the prism. 
Table II.—Series of Isolated Determinations made by Metlioci of Total Keflection. 
No. 
li. 
t. 
IX at 19°. 
Remarks. 
1 
1-34232 
o 
i 
1 — ^ ! 
0 
1-34240 
_ 
— 
1 Some alum crystals placed in the trough. 
o 
O 
1 - 34306 
— 
— 
[ A crystal face adjusted near prism. i 
4 
1-34350 
— 
— 
J The crystal nearer to the prism. 
5 
1-34273 
16-6 
1 - 34250 
16-6° is the air temperature. 
6 
1-34251 
— 
— 
— 
7 
1-34326 
15 
1-34286 
— 
8 
1-34433 
15 
1-34396 
Prism immersed deep in trough. ‘ 
9 
1-34274 
15 
1-34234 
10 
1-34210 
— 
— 
1 Same solution (tvo determinations). 
11 
1-34199 
— 
— 
J 
12 
1-34263 
IH 
1-34210 
Some crystals in trough. 
All these are solutions saturated, or very slightly supersaturated, at the ordinary 
temperature ; but the observations are not represented on Diagram I. because the 
exact composition of the several solutions is not certain. 
Table III. represents a series of observations made upon a supersaturated solution 
of known strength gradually diluted down by addition of water, and determined by 
means of a hollow prism holding about 6 cub. cent 1ms. of liquid. 
These are denoted by small circles on I)iagrain I., and serve to establish 
approximately a curve which shows the relation between composition and refracti^ e 
index in supersaturated and strong solutions of potash alum. 
Table IV. represents a few isolated observations made by the hollow prism upon 
solutions of known strength ; they are denoted by small crosses on Diagram I., and 
serve to check the curve represented in Table HI. 
