HALOID COMPOUNDS OF SILVER, MERCURY, LEAD, AND COPPER. 1167 
25. The effect of the addition of the second molecule of AgT, raising the percentage 
to 55'3066, has been— 
(a) To diminish the coefficient of expansion below 221° C. to ‘00003750. 
(b) To annul the expansion between 221° C. and 233° C. 
(c) To produce contraction on heating between 233° C. and 298° C., viz.: through 
65° O. 
(d) To augment slightly the coefficient of expansion above 298° C., viz.: from 
•00007317 to ‘00009474. 
26. The addition of the third molecule of AgT in Ou 2 I 2 .3AgI raises the percentage 
of iodide of silver to 64*9884, and the effect has been— 
(a) To diminish the coefficient of expansion below 177° C. to, *00002307, and 
between 177° O. and 194° 0. to 00001285. 
(b) To annul the expansion between 194° C. and 214° C. 
(c) To produce contraction on heating between 214° C. and 280° C., viz.: through 
66° C. 
(d) To augment to the same extent as the preceding the coefficient of expansion 
above 280° C., viz.: from *00007317 to *00009474. 
It will be noticed in the case of this alloy, which differs from the preceding one 
(Cu 2 I 2 .2AgI) by containing nearly 10 per cent, more of iodide of silver and nearly 10 
per cent, less of iodide of copper—(1) that the contraction takes place through the 
same range of temperature (65° C.), beginning, however, 19° C. lower; (2) that the 
coefficient of expansion above the point at which contraction finishes is the same; (3) 
that the specific gravity and fusing point are practically the same. In fact, the almost 
sole effect of the additional 10 per cent, of iodide of silver has been to increase the 
coefficient of contraction between 214° C. and 280° O. 
27. The addition of the fourth molecule of Agl in Cu 2 I 2 .4AgI raises the percentage 
of Agl to 71*2225, and the effect has been— 
(а) To diminish the coefficient of expansion below 159° C. to *00001999, and 
between 159° C. and 180° C. to *00001056. 
(б) To annul the coefficient of expansion between 180° C. and 199° C. 
(c) To produce contraction on heating between 199° C. and 282° C., viz.: through 
83° C. 
(d) To augment more than two-fold the coefficient of expansion above 282° C., viz.: 
from *00007317 to *0002050. 
28. The addition of the twelfth molecule of Agl in Cu 2 I 2 .12AgI raised the percent¬ 
age of Agl to 88*1304, and, as might be expected, altered the character of the alloy 
from that of the preceding, approximating it more to the iodide of silver, and 
diminishing the influence of the iodide of copper. The effect has been— 
MDCCCLXXXII. 7 K 
