Sa

Simple Preparations.

burn it in a clofe iron veflel, untill it becomesbkck and friable : afterwards rub it to a veryfine powder.

K.

R E M A R

The gritty matter, compared with the weight ofthe Sponge when prepared, is fometimes confidera-ble.

If the quantity of Sponge put into the veflel atonce beiarge, the outfide will be fufficiently burntbefore the infide is affefted, and the volatile falt ofthe former will in part efcape before that in the laf-ter is begun to be formed. To avoid this incon-venience, the Sponge may be kept continually ftir-ring in fuch a machine as is ufed for the roafting ofcofFee.

Sponge, on diftillation with a ftrong heat, yieldsa volatile falt in its proper form j and, even in thispreparation, the falt is fo far extricated, that, if theburnt Sponge be ground in a brafs mortar, it cor-rodes the metal, fo as to contracl a difagreeabletaint, and fometimes an emetic quality. L.

It (hould, therefore, as direded in the former Dif-penfatory, be powdered in a mortar of glafs orftone. Of this lad fort, the mortars of Mr.

Wsd'gb-