Hydrogen sulphide As

In presence of hydrochloric acid, tin(II) in aqueous solution (1) is precipitated by hydrogen sulphide as brown SnS, and (2) will reduce mercury(II) chloride first to mercury(I) chloride (white precipitate) and then to metallic mercury. 

These gases have lower thermal stabilities than hydrogen sulphide as expected from their enthalpies of formation Table 10.2) and they are consequently more powerful reducing agents than hydrogen sulphide. 

The product crystals find industrial application as a component raw material for optical glass, fibreglass, Braun tubes, electric condensers, barium ferrite, etc. Needles shaped crystals are obtained at high pH, while pillar-shaped crystals are formed at neutral pH. The formation of carboxyl ions is via hydroxy ions at high pH, but at neutral pH it may accompany the production of hydrogen sulphide, as... 

For preparing larger quantities of the hydrosulphide it is more convenient to carry out the reaction in the presence of an excess of the precipitant—say 5 grins, of sodium with a mixture of 10 grms. of absolute alcohol and 100 c.c. of pure dry benzene, more alcohol is added from time to time to keep the ethoxide in soln. until all the sodium is dissolved. This liquid is treated with hydrogen sulphide as before. The reaction seems to be quantitative and to be expressed by the equation C2H50Na+H28=C2H50H+NaHS potassium salt is prepared in a similar manner. 

Hydrogen Sulphide as an Acid. — In the anhydrous condition, whether as gas or liquid, hydrogen sulphide has no acidic properties. When moist or in aqueous solution, however, it behaves as a feeble acid, whence the occasional name hydrosulphuric acid. For the characteristic test with lead acetate paper or for the reddening of litmus paper, the presence of at least a little moisture is essential.3... 

Also, in the preparation of the thiosulphate from sodium sulphide and sulphur dioxide, or from sodium sulphite and hydrogen sulphide, as already described, if sodium hydroxide is first added to the solution in such quantity as to lead to the ultimate formation of the hydrogen sulphide and hydrogen sulphite salts in the proportions mentioned, then the reaction proceeds very smoothly and almost without separation of sulphur. 

The sensitivity of hydrogen sulphide as a reagent for detecting ter-valent arsenic by the yellow colour produced in the presence of hydrochloric acid has been stated in widely different terms 4 the smallest amount thus detected is given as 1 part of As203in 1,024,000 parts of water.5... 

Hydrogen Sulphide as a Precipitant. Pass hydrogen sulphide into solutions of salts of the heavy metals acidified with HC1 take for example a solution of copper chloride. 

Certain micro-organisms may indirectly facilitate the formation of natural pyrites and marcasite by evolving hydrogen sulphide as a product of reduction of sulphates. A considerable number of bacteria, algse, flagellata, and infusoria exhibit this kind of activity.5... 

Preparation of m-Nitroaniline (Section 600).—In a 100-cc. flask dissolve 10 grams of m-dinitrobenzene in 50 cc. of hot alcohol cool the solution under running water so that small crystals are formed, and add 10 cc. of a concentrated solution of ammonia in water. HOOD.—Pass into the solution a rapid stream of hydrogen sulphide as long as heat is evolved by the reaction (Eq.) this requires about one-half hour. Heat on the steam-bath for 10 minutes. Pour the product into 200 cc. of water, filter by suction, and wash the precipitate with water. Put the mixture of m-nitroaniline and sulphur into a beaker, add 100 cc. of water and 20 cc. of concentrated hydrochloric acid, stir, and filter off the residue of sulphur by suction. Set the filtrate... 

The first autotrophes to use the Sun s energy (i.e. photosynthesizers) would also have been prokaryotic anaerobes hving in aquatic environments, and they used hydrogen sulphide as a source of the hydrogen needed for carbohydrate synthesis, yielding sulphur as a byproduct, not oxygen ... 

Sulphur is found widely in nature. Inorganic sulphates can be reduced via sulphide to be incorporated into amino acids. Some micro-organisms can use hydrogen sulphide as a source of sulphur, organo-sulphur compounds may also provide microbial sulphur. 

The preparation of the sulphide from the dihalides by hydrogen sulphide in ammoniacal alcoholic solution requires some care or the reaction goes beyond the stage required and decomposition products result. The dihydroxide probably is first formed, (C6H5)3Sb(OH)2, and this reacts with the hydrogen sulphide as follows —... 

In operation, an autoclave of 6 feet diameter by 21 feet tall is charged with a filtrate liquor of approximately 2 per cent sodium hydroxide (NaOH) to 9 feet depth. This is approximately 19,000 pounds of liquor. To this is added 300 pounds of soda ash to bring the alkaline strength to 3 per cent sodium hydroxide, and 8,000 pounds of cyanamide. The charge is aerated for 15 minutes to eliminate acetylene, phosphine and hydrogen sulphide as completely us possible. The charging door of the autoclave Is then closed and the... 

Fourthly, microbial infections can produce unpleasant odours as microbial by-products build up. Production of hydrogen sulphide (as described above) and various organic acids can result providing the noticeable odours. 

The determination of hydrogen sulphide as methylene blue (3,7-bis(dimethylamino)phe-nothiazine-5-onium chloride) was introduced by Fischer (1883) and has been used for seawater in many investigations. Cline (1969) has closely reviewed and tested the methylene blue method and has suggested several improvements. 

---