46 PREPARATION AND MOUNTING 



in full : It is now well known that one of the products obtained 

 from the naphtha of coal-tar is a volatile, oily substance, termed 

 benzole (or, by French chemists, benzine), whose boiling-point, 

 when pure, is about 1 80 Fahrenheit, which is a perfect solvent for 

 fatty substances. In a capsule, previously warmed on a sand-bath, 

 Mr. Dale mixes with the tallow soundings benzole, whose boiling- 

 point may be about 200, until sufficiently diluted so as to run 

 freely, pressing the lumps with a glass; rod until thoroughly 

 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 supplied with benzole, 

 and the contents of the filter washed to the bottom until that 

 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 resi- 

 due or tarnish ; if grease be present, the washings must be con- 

 tinued 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 com- 

 moner quality may be used, but it is more difficult to dry after- 

 wards. 



Pure benzole being costly, this may appear an expensive pro- 

 cess ; but, with the exception of a trifling loss by evaporation, the 

 whole may be recovered by simple distillation. 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 its ceasing to drop from the condenser, the heat is withdrawn and 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. 



