------------+--------------+--------+------------------ Lead Used. | Silver Lost. | Range. | Percentage Loss. ------------+--------------+--------+------------------ Grams. | | | 10 | 6.5 | 1.0 | 1.62 20 | 7.0 | 1.0 | 1.75 40 | 12.0 | 1.5 | 3.00 60 | 12.7 | 0.5 | 3.17 ------------+--------------+--------+------------------ The loss increases with the lead used. ~Effect of Varying Temperature.~--0.4 gram of silver was cupelled with 20 grams of lead. Temperature. Silver Lost. Range. Percentage Loss. Bright red 7.0 1.0 1.75 Clear yellow 17.3 1.7 4.32 The difference in temperature in these experiments was much greater than would occur even with careless work. ~Effect of Varying Silver.~--20 grams of lead were used in each cupellation. ---------------+--------------+--------+------------------ Silver Taken. | Silver Lost. | Range. | Percentage Loss. ---------------------------------------------------------- Milligrams. | | | 12.5 | 0.7 | 0.2 | 5.6 25.0 | 1.4 | 0.1 | 5.6 50.0 | 1.6 | 0.4 | 3.2 100.0 | 2.9 | 0.3 | 2.9 200.0 | 5.6 | 0.5 | 2.8 400.0 | 7.0 | 1.0 | 1.7 800.0 | 9.7 | 1.0 | 1.2 ---------------+--------------+--------+------------------ It will be seen that, although the quantity of silver lost increases with the silver present, the percentage loss is greater on the smaller buttons. The following results are often quoted:--Cupelling 1 grain of silver with 10 grains of lead, the loss was 1.22 per cent.; 10 grains of silver with 100 grains of lead, loss 1.13 per cent.; 25 grains of silver cupelled with 250 grains of lead, lost 1.07 per cent. The proportion of silver to lead was the same in the three experiments, and the largest button gave the best result. Evidently, if the quantities of lead had been the same in the three experiments (say, 250 grains in each case), the loss on the smaller quantities of silver would appear worse in the comparison. In judging these results, it must be borne in mind that it is difficult to regulate the temperature, &c., in consecutive experiments so as to get exactly similar results, so that the range in consecutive cupellations is greater than that in a batch cupelled side by side. ~Effect of Copper and Antimony.~--0.1 gram of silver was cupelled with 20 grams of lead, and to one batch 0.5 gram of antimony, and to another 0.5 gram of copper was added. Loss in Silver Lost. Range. Percentage.