ON TEACHING CHEMISTRY. 309 
were provided—and such a number would suffice for a large class—the 
cost would be but 181. 
A convenient size of platinum dish to use is one about ? inch deep and 
2 inches wide, weighing, with a light cover, about 20 grams. Ata normal 
FIG. 2: 
price of platinum such a dish would cost about 25s , so that a considerable 
number might be provided for an outlay of 10/. Such dishes not only last 
a long time when properly used, but are of value when damaged (Note A). 
A water oven for drying would cost about 1l.; one of Fletcher’s small 
air ovens for drying costs 17s. 6d. 
Fletcher's Argand Bunsen burners, with tripod, are to be recom- 
mended as superior to the ordinary burners for school work. The smaller 
size costs 2s.; the larger 3s. Suitable black rubber tubing for use with 
these burners, # inch in diameter, costs about 9d. per foot. A pair of 
iron crucible tongs costs 1s. 
The apparatus for measuring the gas evolved on dissolving chalk in 
acid would cost about 7s., including a 500 cubic centim. measuring 
cylinder. 
Glass basins about 3 inches in diameter cost 4d. each ; clock glasses, 
6 inches in diameter, 5s. per dozen. 
50 ce. burettes cost 3s. 6d. each. 
It is unnecessary to refer to the cost of the few remaining articles 
required for the suggested experiments, as they are well known. An ex- 
penditure of 50/7. would certainly cover the cost of apparatus required by 
a class of, say, twenty-four, and which would suffice for the use of several 
such classes. 
Note A.—The unfortunate rise in the price of platinum, which makes 
the purchase of any number of platinum vessels for school use out of the 
question, has led me to make a number of experiments in the hope of 
substituting silver; but, as was to be expected, this has proved to be 
impossible. I find, however, that porcelain may be used, provided that 
the heating be effected in a muffle furnace. Small thin hemispherical 
porcelain capsules may be obtained from the dealers, about the size of the 
platinum dishes specified, which are more suitable than porcelain crucibles 
for the experiment. Such dishes may also be used in studying the effect 
of heat on organic substances, the char being burnt in the muffle furnace. 
