color. It is only by heating the metal with sulphur vapor with admittance of air that the product is of a darker color. “I made experiments to determine if the preparation of Al2S3 and MgS was not possible in the same way as K'S, Na'S, and BaS are made. For example, by melting potassium oxide with sulphur some K2S is formed. However, on doing this with alumina and magnesia, it became evident that magnesium and aluminium have less affinity for sulphur than for oxygen, and the experiment failed. But, matters were changed when a reducing agent was introduced with the sulphur. If a mixture of carbon, magnesia, and sulphur are heated, MgS results, which by treating the product with water goes into solution unchanged. Alumina under similar treatment gave no Al2S3. In place of carbon as a reducing agent I next used hydrogen. By igniting magnesia in a stream of hydrogen and sulphur vapor some little MgS was formed, but the mass of the magnesia was unchanged. The next step was to substitute sulphuretted hydrogen for hydrogen and sulphur separately, but only a little MgS was formed in this way. "Since the sulphates of calcium and barium are reduced to sulphides with very little trouble, it appeared probable that magnesium sulphate, MgSO', should be convertible into MgS by a reducing agent. The attempts to do this were unsuccessful. I heated MgSO1 in vapor of ammonium sulphide, but it underwent no change. Since according to Stammer* K2SO*, CaSO1, and BaSO1 may be reduced to sulphides by carbonic oxide, CO, I tried to Pogg. lxxxii. 135. reduce MgSO4 by this means. The following reaction apparently took place MgSO+4CO MgO+COS,+3CO2. "I then took pure magnesia, filled a porcelain tube with it, and passed carbon bisulphide vapor through it. The apparatus was first filled with hydrogen, then as soon as the tube was bright red the carbon bisulphide flask was warmed, and sulphuretted hydrogen and carbonic oxide began to issue from the tube. The heating was continued till carbon bisulphide condensed in the outlet tube, then the fire was removed and hydrogen passed through the tube till it was cold. The MgS resulting was of a gray color, not melted, but as a crumbly powder. The reaction which took place was probably MgO+2CS2+6H=MgS+3H2S+CO+C. "The carbon was left with the MgS; and, to get rid of it I heated the tube up as before but passed hydrogen and carbonic oxide through, when the hydrogen took up the carbon forming probably some hydrocarbon. "Than says that carbon oxysulphide, COS, is formed by leading carbonic oxide and sulphur vapor through a red-hot tube. The reactions made to take place are MgO+2CS2+CO2=MgS+3CO+3S "The product obtained thus contained 58 per cent. MgS and 42 per cent. undecomposed magnesia. In acting on alumina in the same way, the product obtained is a mixture of Al2S3 and alumina." Jahresb. der Chem., 1867, 155. Reichel next tried the different methods which have been proposed to reduce these sulphides to metal, and thus records his results (see p. 183):— "Petitjean* patented a process in England for reducing A12S3 by hydrogen acting at a high temperature, or by melting it with iron filings. MgS, heated a long time in a current of hydrogen, remained unchanged. I mixed MgS with iron filings, put it in a porcelain crucible, covered with fresh, dry, fine NaCl, and filled the crucible to the rim with carbon. To keep out all oxygen, I put the crucible inside a larger Hessian crucible, filling in between with pulverized charcoal. After heating several hours in a wind furnace, I found a half-sintered mass under the NaCl. This material, on being boiled with water, evolved no trace of hydrogen sulphide but only pure hydrogen. This showed that the iron had taken the sulphur from the MgS. Still, I did not succeed in extracting the free magnesium from it by amalgamation. In the same manner, Al2S3 appeared to be decomposed by iron and heat, but it was also impossible in this case to separate the metallic aluminium out of the mass. Copper effects the reduction as well as iron, forming CuS. "Since magnesium is not sulphurized on ignition in a current of hydrogen sulphide, it appeared probable that MgS might be reduced by ignition in a stream of hydrogen. I first tried a current of illuminating gas, well dried and freed from hydrogen sulphide by a potash tube. In spite of long ignition, the MgS was unaltered. Then I tried hydrogen, but that also was unsuccessful, the MgS would not give up its sulphur to hydrogen at a bright red heat. Since hydrogen alone does not act on MgS, it is hardly * Dingler, 148, 371. to be expected that a hydrocarbon can remove any sulphur from it. "To find how carbonic oxide acted towards MgS, I ignited the latter in a stream of this gas. The magnesium sulphide used contained 56.5 per cent. sulphur and 33.0 per cent. magnesium, or 12.47 per cent. more sulphur than the formula MgS allows. Under these circumstances COS was evolved, recognized by forming barium sulphide and sulphate, when led into baryta water. As soon as these gases ceased coming off, I cooled the tube in a current of carbonic oxide. The material had retained its former color and still readily evolved hydrogen sulphide in moist air or water. But it had lost 12.23 per cent. of its weight. The gas, it appears, had united only with the sulphur in excess of that required to form MgS, and the polysulphide was thus changed to the monosulphide." Reichel makes the following summary :— "The above researches show that magnesium and aluminium can unite with sulphur directly at a high temperature. Also, that MgS and Mg2OS will be formed when magnesia is similarly treated. Alumina is unattacked by sulphur. Alumina and magnesia are changed by ignition in carbon bisulphide to sulphides. When carbon bisulphide and oxide act on magnesia, Mg2OS remains; alumina is unchanged. Magnesia is changed by ignition in hydrogen sulphide to MgS, but the operation is tedious and imperfect. By melting the oxides with sulphur no sulphides can be obtained; with alumina the contemporaneous action of a reducing agent is necessary, while magnesia melted with carbon and sulphur or heated in hydrogen and sulphur vapor becomes MgS. "AS" possesses a yellow color, is with difficulty fusi ble, but fuses to a hard crystalline mass. obtained as a sintered yellow powder. water the following reaction takes place: Usually it is In damp air or A12S3+6H2O=Al2(OH)+3H'S. “It burns in the air to alumina and sulphur dioxide. MgS forms a polysulphide, as we have seen, but Al2S3 does not. “Also, Al2S3 and MgS appear to be reduced at a high heat by metals which have a greater affinity for sulphur, yet it remains to be seen whether this property is technically valuable." Leaving these two experimenters, Fremy and Reichel, we have very few allusions to the subject. Those who have proposed to produce aluminium from A12S3 state merely that they use Fremy's process for preparing the A12S3. We have found an article* in which it is proposed to pass vapor of carbon bisulphide and hydrochloric acid together over ignited alumina, Al2S3 being formed as an intermediate product, and Al'C16 ultimately formed by the action of the acid. The writer states that by passing the first alone over the ignited alumina the gas evolved is mostly COS, though a portion of it is decomposed to sulphur and carbonic oxide. He further states that A12S3 is only slightly acted on by sodium chloride, is unaffected by calcium or magnesium chlorides, slightly acted on by potassium chloride, but readily chloridized by hydrochloric acid. F. Lauterborn (see p. 206) claims in a patented process that by calcining aluminium fluoride with calcium sulphide *Chem. News, Dec. 19, 1873. A |