4S4 BISULPHIDE OF CARBON PEISM. 



Let it boil a few moments and then cool, until all bubbles in tlie 

 mass have disappeared. Heat again cautiously until it is a thin 

 liquid, but do not boil, lest bubbles should again form. Of this 

 liquid spread a thin layer with a small brush along the joint, and 

 repeat this every few hours until a layer is formed all round a few 

 millimetres thick. 



The moisture of the glue evaporates partly into the cylinder, and 

 a thin film of vapour is usually formed within. This may be removed 

 by introducing into the hole of the cylinder a thin tube, which 

 reaches to about the middle of the space within, and then sucking 

 strongly at the end of the tube ; the renewal of the air inside thus 

 produced causes a rapid evaporation of the film of vapour. 



Carbon disulphide emits a peculiar fetid odour, evaporates very 

 easily, and is an extremely inflammable liquid, heavier than water, 

 with which it does not mix ; it is therefore often preserved under 

 a layer of water. Resinous substances are dissolved by it ; for this 

 reason sealing-wax cannot be used for fixing the plates. Care 

 should be taken to have no flame nor glowing bodies near this 

 liquid whilst working with it ; a mixture of its vapour with air is 

 quite as dangerous as one of hydrogen and air. 



The carbon disulphide cannot be drawn from the bottle by means 

 of a pipette, or the pungent vapour would then enter the mouth. 

 If it should have been preserved under water, fill the bottle com- 

 pletely with water so that all air is driven out, close the mouth of 

 the bottle with the thumb, invert the bottle, and, when all the water 

 has ascended to the top, allow the carbon disulphide to escape 

 slowly from the bottle by cautiously removing the finger from the 

 mouth, while holding the neck of the bottle within a large funnel. 

 The air must, previously to inverting the bottle, be driven out com- 

 pletely, for if there remains a space above the liquid filled with air 

 the space will also contain a quantity of the vapour of the carbon 

 disulphide, which exerts a considerable pressure and would cause 

 the liquid to be squirted about when the finger is drawn aside. 

 The funnel should contain a suitably cut filter for retaining any ad- 

 mixtures of water and other substances suspended. This funnel is 

 fixed into an arm of the retort-stand ; another arm, attached to the 

 stand below this one, carries a smaller funnel, so arranged that the 

 liquid may flow from the larger funnel into the smaller, and from 

 the smaller into the prism, into the interior of which the tube of the 

 smaller funnel reaches. If the tube of the smaller funnel is too 

 wide for the hole in the prism, draw out a glass tube, insert the thin 

 end into the prism and the funnel tube into the wider part of this 

 tube. Care must be taken that the liquid escapes very slowly from 



