This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
3CaO + 6S2 = 2CaS5 + CaS2O3.
These dissolve in water, and are separated from any residual lime by filtration. To the filtrate, in an open space or under a chimney, hydrochloric acid is then added, which decomposes these substances with the evolution of sulphuretted hydrogen and sulphurous acid gases, and throws down sulphur in the form of an exceedingly fine powder, which is washed until the washings are tasteless (U.S.P.) and have no acid reaction and cease to give a precipitate with oxalic acid (B.P.), showing that both acid and lime have been removed.
Impurities. - There is a great temptation to fraudulent manufacturers to use sulphuric acid instead of hydrochloric acid. It is not only cheaper but it yields a large product, consisting to a great extent of sulphate of calcium, which is precipitated along with the sulphur instead of remaining in solution like the calcium chloride which is formed when hydrochloric acid is employed.
With Hydrochloric acid, 2CaS5 + 2CaS2O3 + 6HC1 = 3S2 + 2H2O + H2S + 2SO2
3CaCl2. With Sulphuric acid, 2CaS5 + 2CaS2O+3H2SO4 = 3S2 + 2H2O + H2S + 2SO2 + 3CaSO4.
Besides this there are the other impurities which may be present in the sublimed sulphur employed in the process.
Tests. - It should be completely volatilised by heat and leave no residue of sulphate behind. Under the microscope it should exhibit only minute globules of sulphur and no crystals of sulphate. The absence of the impurities contained in sublimed sulphur is ascertained by the tests already given.
Dose. - Of precipitated sulphur, as alterative 10 grs., as laxative 30-60 grs.
Sulphuretted Hydrogen. Hydrogen Sulphide. (H2S;34.) A colourless gas, with a smell of rotten eggs. Used only as a test. Properties. - It precipitates most metals as sulphides from acid solutions, the precipitate with arsenic being yellow; antimony, orange; cadmium, yellow; copper, lead, mercury, and silver, black; bismuth, brown; gold and platinum, brownish black.
Preparation. - By pouring diluted sulphuric acid on sulphide of iron. By passing the gas into cold water a solution is obtained.
General Action of Sulphuretted Hydrogen. - As sulphuretted hydrogen is formed in small quantities from sulphur when the latter is used in various ways, it may be more convenient to take is action before that of sulphur, It is very destructive to plant life even in very minute quantities. There is a curious N N difference between the action of sulphuretted hydrogen and that of sulphurous acid on plants. The latter seems to act as an irritant, causing the leaves to crumple up and fall off, but even when the leaves are destroyed by sulphurous acid the plant may again recover. Sulphuretted hydrogen causes the leaves simply to become flaccid and droop, but when this has once taken place the plant does not recover.
In animals it destroys the functions of all tissues, and in consequence has two actions which are well marked, (1) decomposing the blood and thus producing symptoms of asphyxia, and (2) paralysing the nervous system and muscles. It is absorbed by the skin, by the lungs, mucous membrane of the alimentary canal, and subcutaneous cellular tissue, and may produce symptoms of poisoning through any of these channels. In frogs, which are less affected than mammals by interference with the respiration, the symptoms produced by sulphuretted hydrogen are those of paralysis of voluntary motion and reflex action, preceded by a stage of restlessness. In mammals the symptoms are those of asphyxia; muscular tremors occur, and are succeeded by asphyxial convulsions and death. Most cases of poisoning by sulphuretted hydrogen in man occur from inhalation of the gas which is often found in large quantities in cesspools.
One case has been recorded where symptoms of poisoning occurred from the excessive formation of the gas in the intestinal canal, and subsequent absorption into the blood. Cases of poisoning are best treated by artificial respiration.
Special Action. - Even in minute quantities it destroys the catalytic action of many substances on peroxide of hydrogen. In this respect, as well as in many of the symptoms it produces, it resembles hydrocyanic acid.
On the blood. It first reduces and then decomposes haemoglobin. Both the blood and the muscles of frogs poisoned by it exhibit a greenish colour. As death occurs in mammals before the blood has become so extensively changed, it simply exhibits the characters of asphyxial blood. It induces rigor mortis rapidly in the muscular substance both of the voluntary muscles and of the frog's heart.
Action of Sulphur. - Sulphur, when brought into contact with living protoplasm, enters into combination and forms sulphuretted hydrogen or sulphurous acid. When sulphur is sprinkled over actively-growing fungi, like those which cause the vine-disease, these gases are formed and the fungi destroyed.
Sulphur has little or no action on the skin, excepting a mechanical one. It is a laxative (p. 394). When taken into the intestinal canal, a considerable part of it again passes out unchanged; a little of it, however, appears to be converted into sulphides and into sulphuretted hydrogen. The latter is excreted by the breath, and may give to it the peculiar disagreeable smell of rotten eggs. It is also excreted by the skin, so as to blacken any silver articles which may be worn about the person. The sulphides give rise to increased peristaltic action of the bowels, so that the motions become more frequent and softer; colicky pains are sometimes produced. The sulphides, after absorption into the blood, are excreted in the urine, chiefly as sulphates.
Uses. - For its use in skin disease, vide p. 544. It has been applied by insufflation to the throat in diphtheria, in order to destroy the organisms present in the pharynx, in the same way as in the vine-disease. I have seen one case do very well under this treatment; but its general efficacy is by no means certain. Internally it is employed as a mild laxative in cases of constipation where active purgatives are inadmissible, as in pregnancy, in haemorrhoids, fissure of the anus, and stricture or prolapsus of the rectum. It has been used also in cases of lead-poisoning, to prevent the reabsorption of the lead from the intestine.
It has been found useful in cases of sexual irritation arising from haemorrhoidal congestion (p. 451), and also in the nervous excitement and other disturbances accompanying the menopause.
It exerts a beneficial action on the tissues in chronic rheumatism and gout, and is especially useful in the form of sulphurous waters. During its elimination by the lungs it is supposed to have a beneficial action on them, and it is consequently used in chronic bronchitis.