Max Nitsche-Niesky recommends the following: Good coke is ground and mixed with coal-tar to a stiff dough, and pressed into moulds made of iron and brass. After drying for a few days in a closed place, it is heated in a furnace where it is protected from the direct flames, and burned, feebly at first, then strongly, the fire being gradually raised to white heat which is maintained for 6-8 hours. The fire is then permitted to slowly go down; when perfectly cold, the carbon is taken out of the furnace. (Neu. Erfind.)

The best way is to buy them ready cut from retort scurf; but the following may be useful: - The size of the carbon is the first thing to determine. First satisfy yourself as to the size you wish to make it, and when made let it remain so. Take, for instance, a carbon for use in an ordinary 5 by 7 Fuller or Bunsen battery. Make it, say, 2 by 8 1/2 in. Procure two pieces of sheet iron or brass, preferably brass, but the former will answer, 3 by 10 in., not less than 1/4 in. thick and perfectly flat. Then make, or have made, from a rod of metal 1 in. square and about 22 in. long, a rectangular frame of three sides, whose internal dimensions will be 2 by 10 by 1/2. in. or thereabouts. These three pieces constitute the mould, and in order to complete it, it only remains to place the U-shaped frame between the two plates, fastening the whole firmly together by means of screw clamps, and you will have an oblong box, open at one end. See that the parts fit as closely as possible. Next pulverise in an iron mortar a quantity of gas-retort carbon or common coke, taking care to have a little more than is sufficient to fill the mould. The finer the coke powder the better. Place it in a glass or earthenware dish, and pour upon it a small quantity of syrup or dissolved sugar.

Mix and knead the mass thoroughly with the fingers, adding by degrees a little of the syrup until it becomes sufficiently moist to bind well when pressed together. Set the mould on end, drop in enough of the mixture to fill it about 1/3, and stamp it down lightly with a 1/4 in. rod. Continue the the operation until the mould is full, then get a piece of wood or metal nearly large enough to fit the mould for use as a rammer. Place one end in the opening, and strike it smartly with a mallet. The mass will be driven down about 2 in. and tightly compressed. With a little water mix up some plaster of paris to the consistency of dough, and press it into the opening, having previously removed the rammer. Force it down, and continue adding the plaster till the end is thoroughly closed. The contents of the mould are now ready for the "carbonising" process. Make a good coal fire, place the mould upon it and expose to a red heat for an hour or more. Allow it to remain until the fire has gone out. When cold enough to admit of being handled by the fingers, remove it, .and if the experiment has been properly conducted, you will find the carbon complete.

It is true that a carbon made in this way is not so dense as the commercial article; but for ordinary battery purposes it will be found equal to any, and all that can possibly be desired. (Eng. Meek.) Jacquelain describes three methods of purifying carbon. 1. Treatment with dry chlorine at a high temperature. In this way silica, alumina, magnesia, alkalies, and metallic oxides are removed as volatile chlorides, and the combined hydrogen forms hydrochloric acid. The carbon should be cut into sticks before submitting to this process. The vacuities left in the carbon after treatment with chlorine may be filled up, and the mass made compact, by heating in a closed vessel with some hydrocarbon such as heavy coal oil. In the course of a few hours a sufficient deposit of carbon will have taken place. 2. The carbon may be treated in an iron vessel with fused caustic soda. In this way aluminates and silicates are formed, and may be removed by washing. Dilate hydrochloric acid is next applied to dissolve oxide of iron and earthy bases, and the carbon is finally washed with distilled water. 3. By immersion for 24 hours in hydrofluoric acid diluted with twice its weight of water, carbon may be efficiently purified. The danger accompanying the use of hydrofluoric acid is an objection to this method.

These three processes are applicable to gas-retort carbon or to Russian graphite. The author has also prepared pure graphitoidal carbon from heavy hydrocarbons. It is of excellent quality, but he is unable to state its relative cost. He notes that natural graphite from Siberia gives twice as bright a light when purified as when used in its natural state.