Potassium sulfate

“ The solubility of potassium sulphate does not show the same peculiarities as that of sodium sulphate, because it does not combine with water of crystallisation; at the ordinary temperature 100 parts of water dissolve about 10 parts of the salt, at 0° 8·3 parts, and at 100° about 26 parts. The acid sulphate, KHSO4, obtained easily by heating crystals of the normal salt with sulphuric acid, is frequently employed in chemical practice. On heating the mixture of acid and salt, fumes of sulphuric acid are at first given off; when they cease to be evolved, the acid salt is contained in the residue. ”

“ It forms a liver-coloured mass. In the pharmacopoeia it is designated potassa sulphurata.
Potassium sulphite, K2SO3, is prepared by saturating a potash solution with sulphur dioxide, adding a second equivalent of potash, and crystallizing in a vacuum, when the salt separates as small deliquescent, hexagonal crystals. The salt K2SO3·H2O may be obtained by crystallizing the metabisulphite, K2S2O5 (from sulphur dioxide and a hot saturated solution of the carbonate, or from sulphur dioxide and a mixture of milk of lime and potassium sulphate) with an equivalent amount of potash. ”

“ The oxide is the weakest base of the whole group, yet the oxalate is comparatively readily soluble in mineral acids (compare p. 132) , and the potassium double sulphate is almost insoluble in potassium sulphate. The sulphate is altogether exceptional in that it is very easily soluble in water, and crystallises out with 6 molecules of water of crystallisation. The fluoride and the carbonate both dissolve readily in excess of precipitant, whilst sodium thiosulphate precipitates a basic salt from neutral solutions. ”

“ Some compound substances, when heated upon charcoal, form white incrustations, resembling that formed by antimony, and which, when heated, may, in like manner, be driven from place to place. Among these are certain sulphides, as sulphide of potassium, and sulphide of sodium, which are formed by the action of the reducing flame upon the sulphates of potassa and soda, and are, when volatilized, reconverted into those sulphates, and as such deposited on the charcoal. ”

“ POTASSIUM [symbol K (from kalium) , atomic weight 39·114 O=16) ] , a metallic chemical element, belonging to the group termed the metals of the alkalis. Although never found free in nature, in combination the metal is abundantly and widely distributed. In the oceans alone there are estimated to be 11411012 tons of sulphate, K2SO4, but this inexhaustible store is not much drawn upon; and the “salt gardens” on the coast of France lost their industrial importance as potash-producers since the deposits at Stassfurt in Germany have come to be worked. ”

“ The addition of a sulphide is very dangerous. It is of advantage that the final bath contain an excess of alkali, but only as ammonia or ammonium carbonate. For a copper salt the acetate is preferable. According to this, the solution A is prepared in the warm, and solution B is added with heating. Solution A: Neutral copper acetate, 30 parts, by weight; crystallized sodium sulphite, 30 parts, by weight; ammonium carbonate, 5 parts, by weight; water, 500 parts, by weight. Solution B: Potassium cyanide (98 to 99 per cent) , 35 parts, by weight; and water, 500 parts, by weight. ”

“ Before distilling, a sufficient quantity of potassium sulfid is added to precipitate all the mercury as sulfid and thus prevent the formation of mercurammonium compounds which would produce a deficit of ammonia. A convenient strength of the sulfid solution is obtained by dissolving forty grams of potassium sulfid in one liter of water. Bumping at the end of the distillation is not usual, especially if potash-lye be used, but should it occur it may be stopped by the addition of zinc dust. ”

“ The precipitated sulphide is dissolved in potassium sulphide, and the resultant solution, after warming with a little hydrogen peroxide to discolorize any poly-sulphides that may be present, electrolyzed with a current of 1.5-2 c.c. of electrolytic gas per minute (10.436 c.c. at 0° and 760 mm. = 1 ampere) , when the antimony is deposited as metal upon the negative electrode. One part of antimony (as metal) in 1,500,000 parts of solution may be thus detected, a reaction thirty times more delicate than the deposition by means of zinc and potassium. ”

“ A solution of potassium sulphide of a certain strength is made by igniting 20 parts of potassium sulphate with 6 parts of coal, boiling the mixture with 1·5 time the quantity of rain water, cooling the solution, separating from the potassium sulphate which crystallises out, and boiling the solution with sulphur so long as it is dissolved. ”

“ Standard solutions should not be kept in a place exposed to direct sunlight. Oxidising and reducing solutions, such as those of permanganate of potash, ferrous sulphate, iodine, hyposulphite of soda, &c., gradually weaken in strength; the solutions of other salts are more stable; while those of potassium bichromate and baric chloride are almost permanent. Solutions of potassium permanganate may be kept for a month or so without much change. The solutions of hyposulphite of soda and of iodine should be examined weekly. ”

“ All hydrogen atoms are equal, and equally serve as an object of attack for the atoms of molecules encountering them, but those only are removed from the sphere of action which are nearer the surface of a molecule, which are more mobile, or held by a less sum of forces. So also sulphur is one and the same in sulphur dichloride, in sulphurous or sulphuric anhydride, in hydrogen sulphide, in potassium sulphide, but it reacts differently, and those elements which are with it also vary in their reactions because they are with it, and it varies its reactions because it is with them. ”

“ Potassium sulphide (K2S) is a solid substance, and it is largely due to it that gunpowder gives off smoke and soot when it explodes. Smokeless powder consists of organic substances which, on explosion, give only colorless gases, and hence produce no smoke. Sodium nitrate is cheaper than potassium nitrate, but it is not adapted to the manufacture of the best grades of powder, since it is somewhat deliquescent and does not give up its oxygen so readily as does potassium nitrate. ”

“ Hard soap is a combination of oil or fat, and soda. The quantity of real alkali in potash may be known by the proportion of acid required to saturate a given weight of it. Potash, pearl-ash, salt of tartar, and salt of wormwood are all carbonates of potassa. This alkali is called the vegetable alkali, because it is obtained from vegetables. It is considered to be the hydrated deutoxide of potassium, and when decomposed will furnish potassium.
Table of the saline or soluble products of one thousand pounds of ashes of the following vegetables. ”

“ A subsulphide, Ni2S (?) , results when the sulphate is heated with sulphur or when the precipitated mono sulphide is heated in a current of hydrogen. It forms a light yellow amorphous mass which is almost insoluble in acids. The monosulphide, NiS, is obtained by heating nickel with sulphur, by heating the monoxide with sulphuretted hydrogen to a red heat, and by heating potassium sulphide with nickel chloride to 160-180° C. When prepared by dry methods it is an exceedingly stable, yellowish, somewhat crystalline mass. ”

“ I have devised another method of treating pure sulphate of potash so as to obtain pure hydrate of potash therefrom; it consists merely in operating upon the sulphate of potash in a manner similar to that in which sulphate of baryta is operated upon to procure hydrate of baryta, that is in converting the sulphate into sulphide by the conjoined application of a reducing agent and a red heat, and to decompose the aqueous solution of the sulphide by the action of an oxide of a metal whose sulphide is insoluble, such as oxide of iron (?) , oxide of copper or deutoxide of manganese. ”

“ Unfortunately, bichromate of potash is not very soluble in water; one pint of water will not take up much more than three [Pg 47] ounces of this salt. Hence, though the solution of potassium bichromate is an excellent depolariser as long as it contains any of the salt, it soon becomes exhausted. When bichromate of potash is used in a cell along with sulphuric acid and water, sulphate of potash and chromic acid are formed, thus:—
From this we learn that before the potassium bichromate enters into action in the battery, it is resolved into chromic acid. ”

“ The elements of cyanogen, combined with sulphur, form a salt radical, sulphocyanogen, C2NS2, which is expressed by the symbol Csy. The sulphocyanide of potassium, KCsy, is prepared by fusing ferrocyanide of potassium, deprived of its water of crystallization, intimately mixed with half its weight of sulphur and 17 parts of carbonate of potassa. The molten mass, after having cooled, is exhausted with water, the solution evaporated to dryness, and extracted with alcohol, from which the crystals of the salt are separated by evaporation. ”

“ It requires more than 1200 parts of water for its solution: for its perfect purification, it should be heated with a solution of chloride of potassium, the insoluble portion separated whilst the liquid is lost, and the peculiar salt allowed to deposit as the temperature falls. When heated, it behaves like the salt of silver. ”

“ Solution of potash is stated to convert the resin of sumbul into a crystalline potassium salt of Sumbulamic Acid, which latter was obtained in a crystalline state by Reinsch in 1843, but has not been further examined. Sumbulamic acid, which smells strongly of musk, appears to be a different substance from Sumbulic or Sumbulolic Acid, the potassium salt of which may be extracted by water from the above-mentioned alkaline solution. ”

“ At 32° F. it is brittle, like glass; at 59° it is soft and malleable; at 144° it becomes liquid. Potassium is widely diffused in the vegetable, animal and mineral kingdoms. Some of the more important potassium compounds are caustic potash (the hydroxide) , the carbonate, the bicarbonate; also potassium chloride, bromide, iodide, nitrate (saltpeter) , sulphate, chlorate, cyanide etc. Of these iodide, bromide and chlorate are used for medicines, the others being employed more or less in the arts. ”

“ The cheapest process is to ignite potassium bichromate with sulphur, extract the mass with very dilute sulphuric acid and wash the residue. The chromic acid is reduced by the sulphur; when the mass is treated with sulphuric acid sulphur dioxide is evolved, potassium sulphide and sulphate are dissolved, whilst pure chromium oxide remains. The larger the quantity of sulphur used the paler is the chromium oxide. The purity of the potassium bichromate has considerable influence on the shade of the pigment; if iron is present in any quantity a discoloured product always results. ”

“ The sodium salt does not crystallise and is very unstable: the barium salt is, however, more stable. The barium and potassium salts are anhydrous, they give neutral solutions and decompose when ignited, with the evolution of sulphur and sulphurous anhydride, a sulphate being left behind, K2S3O6 = K2SO4 + SO2 + S. If a solution of the potassium salt be decomposed by means of hydrofluosilicic or chloric acid, the insoluble salts of these acids are precipitated and trithionic acid is obtained in solution, which however very easily breaks up on concentration. ”

“ Bi, 81·25 per cent., S, 18·75 per cent., occurs, in the course of analysis, as a brownish-black or quite black precipitate, insoluble in water, dilute acids, alkalies, alkaline sulphides, sulphate of soda, and cyanide of potassium, but dissolving in moderately concentrated nitric acid with separation of sulphur. It continually increases in weight when dried in the ordinary way, and is completely reduced when fused with cyanide of potassium. ”

“ The term potash is commonly used to designate any of the salts of the element potassium, particularly those soluble in water, which are largely used in agriculture and manufacturing. The element potassium is widely distributed as a component of rocks, soils, and vegetable and animal substances, but large quantities of potassium salts in forms suitable for the uses of man have been found in only a few places. Ashes of wood, which were formerly the principal source of potash in commerce, now supply an inconsiderable part of the world’s requirements. ”

“ When mixed with a weak solution of sulphate of indigo, and heated, the colour of the latter is destroyed.—6. When saturated with carbonate of potassium or sodium, and evaporated to dryness, the residuum deflagrates when thrown on burning coals.—7. When the mixture of a nitrate with cyanide of potassium, in powder, is heated on a piece of platinum, a vivid deflagration follows, attended with distinct ignition and detonation. (Fresenius.) It is stated that sulphate of aniline is an extremely delicate test for nitric acid. ”

“ Sulphide of ammonium gives similar reaction. Ammonia and potassa produce bulky reddish-brown precipitates insoluble in excess. Ferrocyanide of potassium gives a rich blue precipitate, insoluble in hydrochloric acid, and readily decomposed by potassa. Ferricyanide of potassium deepens the colour, but does not give a blue precipitate, as it does with ferrous salts (proto salts) . Sulphocyanide of potassium gives an intense ruby-red colour to neutral or acid solutions. Tincture and infusion of galls strike a black colour. ”

“ The sulphate of potassium of commerce is a secondary product of several chemical and manufacturing processes. Thus, the residuum of the distillation of nitric acid from nitre is dissolved in water, the solution neutralised with carbonate of potassium, and, after defecation, evaporation until a pellicle forms ”