94 



CHEMISTRY. 



stance are taken, placed between folds of fil- 

 tering-paper, and pressed between hot plates ; 

 the remainder of the substance is repeatedly 

 boiled with alcohol, washed with cold alcohol 

 upon a filter, and next dried and weighed. 

 The fusion-point of the mass should be, as 

 near as possible, 210. The author says that 

 sulphide of carbon is not well suited for the 

 purification of anthracen, because that sub- 

 stance is too readily soluble in that fluid. 

 100 parts of alcohol dissolve, when cold, 0.6 

 parts of anthracen ; 100 parts of cold benzol 

 dissolve 0.9 parts of anthracen ; and 100 parts 

 of sulphide of carbon dissolve 1.7 parts of 

 anthracen. 



Improved Method of making Lead Paints. 

 A patent has been received by Messrs. Dale 

 & Milner, of England, for the invention of an 

 improved method of manufacturing white-lead 

 (carbonate) by the action of the soluble acid 

 carbonates of the alkalies on litharge, hydrated 

 oxides of lead, or insoluble basic salts of lead. 

 The patentees propose to carry out their in- 

 vention in two ways, and, when soda is the 

 substance chosen, they proceed 1. By mix- 

 ing litharge, hydrated oxides of lead, or insol- 

 uble basic salts of lead, with an equivalent of 

 bicarbonate of soda, together with sufficient 

 water to form a stiffish paste. This mix- 

 ture is ground in a suitable mill, small quanti- 

 ties of water being from time to time added 

 as may be found requisite until the change of 

 the lead bodies into carbonates is complete. 

 The paste is now well washed with water, 

 and the supernatant liquid which contains 

 monocarbonate of soda is separated from the 

 white-lead by filtration, and boiled down to 

 dryness, and disposed of as soda-ash; or it 

 may be crystallized; or it may be again con- 

 verted into bicarbonate of soda, by treatment 

 with carbonic acid, and u%ed to convert fur- 

 ther quantities of lead oxides, or insoluble 

 basic salts of lead, into carbonates. Instead 

 of grinding, the lead oxides, or insoluble basic 

 salts of lead in a fine state of division, may 

 simply be mixed with bicarbonate of soda and 

 water and left to themselves, when the con- 

 version into carbonates goes on in the same 

 manner, only much more slowly. 2. They 

 mix litharge, hydrated oxides of lead, or basic 

 salts of lead, with caustic soda, monocarbonate 

 of soda, or acid carbonates of soda, and suffi- 

 cient water to form a stifHsh paste. The mix- 

 ture is now introduced into a suitable closed 

 mill, and during the grinding a stream of car- 

 bonic-acid gas is passed into it. After con- 

 version of the lead bodies into carbonates, they 

 are washed with water, and the supernatant 

 liquid treated as before described. In carry- 

 ing out their process by this secondly de- 

 scribed method, the patentees do not bind 

 themselves to any particular proportion of 

 lead oxides and soda, but equivalents of each 

 answer very well. The quantity of the soda 

 salts may, however, be reduced with advan- 

 tage if found desirable. Grinding may also 



be dispensed with, by mixing the lead oxides 

 or insoluble basic salts of lead in a fine state 

 of division with the caustic soda, monocar- 

 bonate or acid carbonates of soda, as described, 

 and exposing the mixture in a suitable room 

 to the action of carbonic acid. Artificial heat 

 accelerates the conversion, both in the first 

 and secondly described operations, but is not 

 essential to their success. The patentees claim 

 the manufacture of carbonate of lead by the 

 action of acid carbonates of the alkalies on 

 litharge, hydrated oxides of lead, and insolu- 

 ble basic salts of lead, either by direct addi- 

 tion, as described in their first part, or indi- 

 rectly by the mixture of the lead oxides with 

 the caustic alkalies, or their monocarbonate 

 or acid salts, and their conversion into bicar- 

 bonates during the time they are in contact 

 with the litharge, hydrated oxides, or insol- 

 uble basic salts of lead. 



Manufacture of Sulphide of Carbon. In 

 1840 rectified sulphide of carbon cost per kilo- 

 gramme fifty francs, in 1848 eight francs, and 

 now by the improved method of manipulation 

 only fifty centimes. The apparatus employed 

 consists of vertical retorts made of the same 

 kind of clay as is in use for glass pots, lined in- 

 ternally with a glaze composed of one hundred 

 and thirty parts of flint glass, twenty parts of 

 carbonate of soda, and twelve parts of boracic 

 acid fused together, and next pulverized and 

 painted on the inside of the retorts with gum- 

 water (at the first heating of the retorts this 

 mixture yields a glaze which entirely closes the 

 pores of the material, thus preventing escape 

 of vapors and gases) ; four of these retorts are 

 set in one oven made of brickwork, and are 

 heated by a properly-constructed furnace ; the 

 retorts are provided with the necessary tubes 

 for the abduction of the vapors of the sulphide 

 of carbon, and the introduction of the charges 

 of sulphur and charcoal ; the operation once 

 commenced is continuous, since the retorts last 

 for at least six months ; the consumption of 

 sulphur per retort amounts to 125 kilogrammes 

 in twenty-four hours, introduced in charges of 

 155 grammes each, every three minutes time ; 

 the vapors of the sulphide of carbon are col- 

 lected and condensed in vessels made of zinc 

 or sheet-iron, and shaped like flattened-down 

 casks, and entirely covered over with cold wa- 

 ter constantly refreshed, while the contrivance 

 is so arranged as to keep the sulphide under 

 water also (its specific gravity is 1.265). The 

 ^most suitable temperature for this manufac- 

 "ture is bright-red heat; the raw liquid ob- 

 .tained has to be redistilled, and this opera- 

 tion is conducted in large iron vessels, which 

 contain some 5,000 kilogrammes at the same 

 time and communicate with six worm con- 

 densers ; steam is used for heating by means 

 of a serpentine-coiled set of pipes, and the 

 liquid is heated to 48 ; near the end of the 

 distillation the temperature is raised to 100, 

 in order to drive off a raw product con- 

 taining very much sulphur dissolved ; in the 



