1823.] Vegetable and Animal Substajtces. 347 



tube, and may be slid along, and left at any part of the serni- 

 cylindric cage, so as to preserve from the influence of the heat 

 any requisite portion of the sealed end of the tube." 



For the analysis of volatile liquids, Dr. Ure employs a little 

 bulb, which, after it has been filled and exactly weighed, " is 

 immediately slid down to the bottom of the tube, and covered 

 with 1 50 or 200 grains of peroxide of copper. The bulb has a 

 capacity equal to three grain measures of water, and its capillary 

 point is sometimes closed with an inappreciably small quantity 

 of bees' wax, to prevent the exhalation of the liquid, till the per- 

 oxide be ignited." 



The furnace is provided with a cover, with an oblong orifice 

 at its top, which serves for a chimney, " and may be applied or 

 removed by means of its handle, according as we wish to increase 

 or diminish the heat, c c c c are tin cases inclosing corks, 

 through which the iron wires are passed, that support the whole 

 furnace at any convenient height and angle of inclination." 



" The tightness of the apparatus at the end of the process is 

 proved by the rising of the mercury in the graduated receiver, 

 by about one-tenth of an inch, as the tube becomes refri- 

 gerated." 



" My mode of operating with the peroxide of copper," conti- 

 nues Dr. Ure, " is the following : 



" I triturate very carefully in a dry glass mortar from one to 

 two and a half grains of the matter to be analyzed, with from 

 100 to 140 grains of the oxide. 1 then transfer it by means of a 

 platinum-foil tray and small glass funnel, into the glass tube, 

 clearing; out the mortar with a metallic brush. Over that mix- 

 ture, I put 20 or 30 grains of the peroxide itself, and next, 50 or 

 60 grains of clean copper filings. The remaining part of the 

 tube is loosely closed with 10 or 12 grains of amianthus, by 

 whose capillary attraction the moisture evolved in the experi- 

 ment is rapidly withdrawn from the hot part of the tube, and the 

 risk of its fracture thus completely obviated. The amianthus 

 serves moreover as a plug, to prevent the projection of any 

 minute particles of filings, or of oxide, when the filings are not 

 present. The tube is now weighed in a very delicate balance, 

 and its weight is written down. A little cork, channelled at its 

 side, is next put into the tube, to prevent the chance of mercury 

 being forced backwards into it, by any accidental cooling or 

 condensation. The collar of caoutchouc is finally tied on, and 

 the tube is placed, as is shown in fig. 1, but without the plate k, 

 which is employed merely in the case of analysing volatile 

 liquids. A few fragments of ignited charcoal are now placed 

 under the tube at the end of the furnace next to the cistern, and 

 the remaining space in the semi-cylinder is filled up with bits of 

 cold charcoal. The top may then be put in its place, when 

 the operation will proceed spontaneously, the progressive advance 



