The best mode of preventing nuisance from calcination is in operation at Shackell & Edwards’ works, in Hornsey Road, Islington. At these works the black is calcined in a chamber 20 feet square and 25 feet in greatest height, with a paved floor and arched roof. In the centre of the roof is the opening where a fire was formerly placed, but which is now closed by a sky-light, capable of being raised. The calcining pots are ranged round this chamber, and a fan, employed to draw off the vapours from the oil-boiling pans, is further utilised to draw off also, from the upper part of the calcining-house, the vapours arising from the calcination, and to drive them into the boiler fire, where they are consumed. Calcination should always be conducted in a closed building duly ventilated so as not to create nuisance. The transport of lamp-black is effected in barrels or bags; when in the latter, these should be previously soaked in water containing some clay in suspension, which stops up the pores of the sacking, and thereby prevents loss. The particular virtue of lamp-black as a pigment lies in its state of extremely fine division, which could not possibly be attained by artificial means; this quality renders it invaluable as the basis of black pigments, all of which contain it in a greater or less quantity. Indian ink and printers’ ink are also composed principally of this substance. =Unimportant Blacks.=--In addition to the recognised blacks already noticed there are a number of other sources of black pigment which have been drawn upon to a limited extent, or have been suggested as substitutes for the standard articles. They only merit a short description. _Aniline black_ is prepared by adding an acidified (sulphuric) solution of bichromate of potash to an aqueous solution of hydrochlorate of aniline, and washing the precipitate. The cost is prohibitive. _Candle black_ is candle smoke condensed on a cold plate. _Charcoal black_ is finely-ground wood charcoal. _Coal black_ has been suggested by grinding coal, but lacks the requisite qualities of a pigment. _Cork black_ is a very fine pigment prepared by calcining cork refuse. Limited supply. _German black_ is Frankfort black. _Iron black_ is ground black sulphide of iron. _Lead black_ is prepared by boiling lead fume in sulphide of soda solution. It would probably be unstable on account of oxidation. _Manganese black_ is ground oxide of manganese. It is costly, and dries too quickly. _Prussian black_ is calcined Prussian blue. It is not of a good colour, nor economical. _Prussiate black_ is the carbonaceous residue from making yellow prussiate of potash. Used chiefly for decolorising syrups, &c. _Spanish black_ is cork black. _Tannin black_ is proposed to be made by exhausting the tannin from refuse leather and tanning agents, and adding alum and sulphate of iron. The colour is blue-black, weak, and unstable. CHAPTER III. BLUES.