The device shown in the accompanying sketch has been in use in the Chemistry Department of the University of Edinburgh for some time. It consists of a silica plate, 5 inches square, with a hole bored in it of such size as to admit a crucible to one-half of its depth. The silica plate is held in an inclined position by a clamp.

By this means the flame gases are excluded from the interior of the crucible during an ignition. With this device calcium carbonate in a platinum crucible is quickly reduced to oxide with a good bunsen burner, while with a Mecker burner the reduction is complete in a few minutes even when a porcelain crucible is used. The device is also useful for cases such as the ignition of nickel oxide, where there is a danger of reduction. For the estimation of sulphur in coal some such device is absolutely necessary to exclude the flame gases.