76 PREPARATION AND MOUNTING 



mingled ; the solution and its contents are then poured into 

 a paper filter, placed in a glass funnel ; the capsule is again 

 washed with benzole, until the whole of the gritty particles 

 are removed into the filter. A washing-bottle is then sup- 

 plied with benzole, and the contents of the filter washed to 

 the bottom until the liquid passes off pure, which may be 

 tested by placing a drop from the point of the funnel on a 

 warm slip of glass or bright platinum, when, if pure, the 

 benzole will evaporate without residue or tarnish ; if grease 

 be present, the washing must be continued until they are 

 free from it. After rinsing through weak acid, or alcohol, 

 for final purification, the calcareous forms will be ready for 

 mounting. 



The filter and its contents may be left to dry spontaneously, 

 when the latter can be examined by the microscope. Should 

 time be an object, rapid drying may be effected by any of 

 the usual methods; one of which, recommended by Mr. 

 Dale, is to blow a stream of hot air through a glass tube 

 held in the flame of a Bunsen's burner. The lower the 

 boiling-point of the benzole, the more readily can the 

 specimens be freed from it. A commoner quality may be 

 used, but it is more difficult to dry afterwards. 



Pure benzole being costly, this may appear an expensive 

 process; but, with the exception of a trifling loss by 

 evaporation, the whole may be recovered by simple dis- 

 tillation. The mixture of tallow and benzole being placed 

 in a retort in a hot-water, a steam, or a sand bath, the 

 benzole will pass into the receiver, and the tallow or other 

 impurities will remain in the retort. When the whole of 

 the benzole has distilled over, which is ascertained by its 

 ceasing to drop from the condenser, the heat is withdrawn 

 and the retort allowed to cool before the addition of fresh 

 material. Half a dozen to a dozen filters, each with its 

 specimen, can be in process at the same time ; and the dis- 

 tillation of the recovered benzole progresses as quickly as 

 the filtration, which was practically proved on the occasion 

 named. The process is very dangerous and great caution 



