A VISIT TO A BONE BOILING. FACTORY. 143 



2| cwt. of charcoal, is of a deep black in colour, and charred in 

 appearance. The charcoal is put in square wrought-iron cases carefully 

 sealed, to cool, which occupies about 10 hours. After cooling, it is 

 elevated by a steam platform, which can be raised, lowered, and stopped 

 at a moment's notice, and as we were elevated from the ground floor 

 to the crushing room by it, can testify as to its practicability. The 

 charcoal, when cool, is crushed in horizontal mills of cast iron, at the 

 rate of about one ton per hour. It has to pass through two mills 

 in order to be crushed sufficiently fine, l-6th to l-8th of an inch square 

 or diameter ; the finest or dust is again re-crushed between two hori- 

 zontally revolving stones called French burrs. This last is used for 

 making ivory black, a chief ingredient in blacking. The main use of 

 the animal charcoal is as a purifier for sugar, but as the charcoal retains 

 superficially some of the tenacious matter of the sugar as well as the 

 impurities, it is found requisite to reburn the charcoal. For this pur- 

 pose revolving retorts are used of the following dimmensions : inside 

 length, 9 feet, inside diameter, 3 feet 9 inches ; number of revolutions, 

 1 in 3 minutes ; power required, 1 nominal horse to each retort. Those 

 at Messrs. Cowan's are their own patented invention, and certainly 

 display great conception on their part. The impure charcoal is washed 

 and put into the retort at the front end by a door, 14 cwt. occupying 13 

 to 14 hours to effectually revivify, when it is taken out into square cases 

 on trucks, and put into another compartment to cool, the top part being 

 sprinkled with water to prevent the air from mixing with it. After re- 

 maining 10 or 12 hours, it is laid on the floor to a depth of about 3 to 

 6 inches, and allowed to effectually cool, after which it is put into bags 

 of 1 cwt., and sent by barges to the respective city customers, the 

 refiners, who pay only an agreed price for the use. We were surprised 

 to find that the gas from the charcoal was treated as that from coal, and 

 used to light up the entire factory, offices, &c, We were also told that 

 the ammoniacal liquor was converted into sulphate of ammonia, by 

 evaporation in open pans. 



Many are the uses to which bone-ash is applied. When ground to 

 moderately fine powder, it is the material of which the cupels of the 

 gold and silver assayers are made, being at the same time very infusible 

 and sufficiently porous to absorb the litharge and other impurities, 

 while the fine metal remains on its surface. 



When levigated and washed over, it forms an exceedingly useful 

 polishing powder for plate and other articles. It is likewise the only 

 material from which phosphorus is at present prepared. Part of the 

 phosphoric acid is separated by the action of sulphuric acid from the 

 lime with which it is combined in the bone-ash ; and this portion, when 

 mixed with charcoal powder and strongly heated in an earthenware 

 retort, is decomposed; the phosphorus is liberated in the form of 

 vapour, and is consolidated by coming in contact with the cold water in 



