162 T H E J O U R N A L OF Ir\TDUSTRIAL A N D ENGIhTEERIh’G C H E M I S T R Y Feb.. 1913

use of respirators, overalls, enforced cleanliness, and the avoidance of lead dust. No material increase in the cost of manufacture has resulted, but death and suffering have been averted. Plumb- ism is usually easy to diagnose, yet lead occasionally induces obscure affections of the nervous system, the cause and true nature of which are not always recognized. The grinding of white lead‘with oil was formerly a large source of lead poisoning, because the pigment was dry, and consequently the grinding mill attendants and the lead work laborers inhaled lead carbonate dust; but since in many factories the paint is noli- made with the lead carbonate in the moist state, by gradually displacing the moisture with oil during the process of grinding, this source of danger has decreased. There is said to be more danger in the process of grinding basic lead sulfate into paint oil than there

position to enter into an alloy with tantalum on its surface, hence there is no need of the cathode being plated with copper or silver as in the case of a platinum cathode. The insensi- bility of tantalum to aqua regia permits the removal of platinum and gold precipitate by that acid. A further advantage of tanta- lum over platinum is its greater strength and rigidity which prevents the electrodes from getting out of shape by bending. The difference in price is noteworthy, that of tantalum being 40 per cent. less than that of platinum. There is also a saving in weight of about 30 per cent. Brunck considers that tantalum may serve as a substitute for platinum in the different types of bleaching electrolyses.

SULFUR IN ILLUMINATING GAS is when grinding the moist lead carbonate in oil. sizes the dangers these being referred to as “terrible.”

Line empha- to the manufacture Of red leads

L, J. wil1ien ( G ~ ~ 31, N ~ , I, 5 ) out that in a plant, where both coal gas and carburetted water gas are manufactured, a high percentage of sulfur in the coal has a twofold, and possibly

TANTALUM AS A SUBSTITUTE FOR PLATINUM I n a paper on “Tantalum Electrodes,” published in the Chem-

iker-Zeitung, 36, No. 126, 1233, 0. Brunck discusses the substi- tutes for platinum and the employment of tan,alum as a partial substitute for this costly yet valuable metal.

As there is little prospect that the price of platinum will ever decline to any considerable extent, science and industry have made strenuous efforts to obtain a substitute. Quartz glass at a moderate price offers, for certain purposes, a substitute for platinum, although not quite its equivalent. It is resistant to acids, with the exception of hydrofluoric acid, and is insensible to sudden changes of temperature, but it is breakable and is a poor conductor of heat. Chemical apparatus has also been made of an alloy of 90 per cent. gold and IO per cent. platinum; this alloy is harder and tougher than gold, but is, unfortunately, more difficult to work than either one of the component metals. It is likely that it might replace platinum entirely if its melting- point were higher; as i t is, its scope of application is large enough, but the economy attained is small, for the price of apparatus constructed of i t amounts to about two-thirds of that of platinum, owing to the higher cost of molding.

A German concern has recently proposed tantalum, originally intended only for the manufacture of metal filaments for electric incandescent lamps, as a partial substitute for platinum, and has put on the market various forms of apparatus and instru- ments made out of that metal at a price of $0.625 per gram, including cost of molding. As a materidl for surgical and dental instruments tantalum has already found favor with practitioners; but in chemical laboratories, tantalum dishes are, so far, the only form in which the metal is employed. Brunck states that the sensibility of tantalum to oxygen a t the higher temperatures and to hydrofluoric acid prohibits a more general use of the metal as a platinum substitute. In a vacuum tantalum will stand the highest white heat, but, heated in the air, it commences to oxidize below a red heat; and while it is perfectly resistant to water solutions of alkalies, the compact metal is destroyed by fused alkalies.

Experiments conducted by Brunck showed that tantalum could be substituted for platinum as cathode material without reserve, while this was not the case with regard to anodes. He found, however, that if it was desired to use tantalum as anode material and to work with a tantalum cathode and a platinum anode, the tantalum anode might be plated with a thin layer of platinum which could be easily accomplished electrolytically. A coating of a few centigrams of platinum was found to suffice. It was found to be even better to employ a n anode of tantalum wire which was plated with platinum by a process patented by Siemens and Halske. Brunck reports that tantalum has even some advantages over platinum as cathode material; for example, zinc and cadmium show no dis-

threefold, evil effect, namely: (I) In almost every case a high sulfur content of the gas will be found, both in hydrogen sulfide and carbon disulfide; ( 2 ) When the coke is used in the generator of a water gas machine, about 50 per cent. of the sulfur in the coke goes into the gas, so that the sulfur which is not given off in the coal gas will be given off in the water gas; (3) A coal containing a high percentage of sulfur usually contains a high percentage or iron, which will cause clinkering trouble when the coke is used in making water gas. By knowing the percentage of sulfur in a coal or coke, the amount of sulfur com- pounds that the unpurified gas will contain can be approximately estimated in the following manner: With coal gas, multiply the percentage of sulfur by 20 and @e product will be grains per IOO cubic feet of sulfur compounds in the unpurified gas. With water gas, multiply the percentage of sulfur in the coke by IO and the product will represent grains of sulfur compounds per 100 cubic feet.

In using lime for removing carbon disulfide, while i t is neces- sary to remove the carbon dioxide from the gas, still i t is not economical to remove carbon dioxide by passing through a lime box. With six purifying boxes connected so that they can be used in any combination, the most economical method of operation is to fill four of them with oxide and two with fresh lime; allow the crude gas to pass through one of the fresh lime boxes for 24 hours to partially sulfide the lime; have the gas pass through two oxide boxes first, in order to remove hydrogen sulfide, then through the fresh lime to eliminate carbon dioxide, then through the lime box containing partially sulfided lime to remove carbon disulfide, and finally pass through one of the other two boxes filled with oxide, keeping one oxide box in readiness to be cut in when necessary. Where the amount of sulfur compounds allowed in the gas is limited to 30 grains per JOO cubic feet, i t is hardly safe to use a coal containing more than 2 per cent. of sulfur and keep within the limit by using lime. Where the limit is 20 grains, the coal used should not contain more than 1.5 per cent. of sulfur.

THE USE OF GASES FOR FIRE EXTINCTION ON BOARD SHIP

A discussion on the use of gases for fire-extinction and fumiga- tion on board ship took place at the meeting of the British Institute of Marine Engineers on November 25, 1912. A re- port of such parts of this as are of interest to the chemical engi- neer is presented below.

G. Canning said he thought that the practice of blowing steam into the cargo could be regarded only as a check to initial Qut- breaks. It had been said that the danger to human beings of systems in which odorless gases were used, could be overcome by impregnating the gas, but such a procedure depended a great deal upon the operator. Canning considered that the possibility of a deposit taking place in the pipes was more likely