Calcium sulfate

“ The soil is completely extracted by diluted hydrochloric acid and the sulfuric acid precipitated in the solution with barium chlorid. If a soil is very rich in calcium sulfate it should first be treated with a warm solution of sodium carbonate to decompose the calcium sulfate, and the sulfuric acid determined in the solution after having added hydrochloric acid. ”

“ Three compounds, viz. the sulfate, chlorid and carbonate of sodium, usually form the main mass of these saline efflorescences. Magnesium sulfate (Epsom salt) is in many cases a very abundant ingredient; some calcium sulfate is nearly always present, and calcium chlorid is not infrequently found.
In some cases the above salts are in part at least derived from the leaching of adjacent or subjacent geological deposits impregnated with them at the time of their formation. Such is the case in portions of Wyoming, Colorado and New Mexico, in the Colorado river delta, and in the Hungarian Plain ”

“ In laboratories which have no means of securing so high a temperature as is mentioned before, the lime may be weighed as sulfate. For this purpose the calcium oxalate is transformed into carbonate by ignition in a platinum crucible. Afterwards it is treated with nitric acid until the carbon dioxid is completely driven off. The platinum crucible is now covered with a funnel which is afterwards washed in order to bring back into the dish the small drops which have been projected in the process of boiling. An excess of sulfuric acid is added and evaporated to dryness on a sand-bath. ”

“ Bilious people have too little sodium sulfate, the melancholics are lacking in potassium sulfate and phosphate; too little calcium phosphate in the phlegmatics. Courageous natures have an excess of iron phosphate. ”

“ A part of the iron sulfate formed reacts with the acid calcium phosphate present to produce a permanent jelly-like compound, difficult to dry and handle. As much as two per cent of iron phosphate, however, may be present without serious interference with the commercial handling of the product. By using more sulfuric acid as much as four or five per cent of the iron phosphate can be held in solution. Larger quantities are very troublesome from a commercial point of view. ”

“ Easily destructible organic matter tends to lower the result, but not materially, unless present in large excess. Calcium carbonate and sulfate, soda, and other alkalies, in the quantities in which they are usually present in water, do not affect the result. The following reagents are required:
1. Concentrated sulfuric acid. 2. An acetic acid solution of carbazol; diphenylimid, (C6H4
C6H4/ NH.) 3. A sulfuric acid solution of carbazol. 4. Standard solutions of potassium nitrate. 5. A solution of aluminum sulfate. 6. A solution of silver sulfate. 1. ”

“ The tests for sulphate of lime in paper ash are based upon the following reactions:—
Calcium sulphate is soluble in dilute hydrochloric acid. The addition of a few drops of barium chloride to the solution produces a dense heavy precipitate, indicating the sulphate. A small quantity of ammonium oxalate solution added to another portion of the dissolved calcium salt previously neutralised with ammonia produces a precipitate and indicates calcium. ”

“ The metals of the alkaline earths, like those of the alkalis, form several compounds with sulphur; thus calcium forms compounds with one and with five atoms of sulphur. There are doubtless also intermediate sulphides. If sulphuretted hydrogen be passed over ignited lime it forms water and calcium sulphide, which may also be formed by heating calcium sulphate with charcoal, whilst if sulphur be heated with lime or with calcium carbonate, then naturally oxygen compounds (calcium thiosulphate and sulphate) are formed at the same time as calcium sulphide. ”

“ Thus calcium forms not only calcium sulphide, CaS, but also as bi-, tri-, and pentasulphide, CaS5, and all these compounds are soluble in water. Sodium also combines with sulphur in the same proportions, forming sulphides from Na2S to Na2S5. If an acid be added to a solution of a polysulphide, it gives sulphur, sulphuretted hydrogen, and a salt of the metal. For instance, MS5, + 2HCl = MCl2 + H2S + 4S. If we reverse the operation, and pour a solution of a polysulphide into an acid, sulphur is not precipitated, but an oily liquid is formed which is heavier than water and insoluble in it. ”

“ The thorough removal of the sulphur is thus brought about by the deoxidation of the calcium. It is by forming calcium sulphide that sulphur is removed in the manufacture of pig iron in the iron blast furnace, in the crucible of which, as in the electric furnaces, the conditions are strongly deoxidizing. But in the Bessemer and open-hearth processes this means of removing sulphur cannot be used, because in each of them there is always enough oxygen in the atmosphere to re-oxidize any calcium as fast as it is deoxidized. ”

“ Sulphate of lime, or “pearl-hardening,” is usually sufficiently pure to put direct into the engine. It is made by decomposing a solution of calcium chloride, with sulphate of soda, and is precipitated as a fine brilliantly white powder, consisting of CaSO4 + 2 H2O.
Two distinct forms of precipitated calcium sulphate are met with in commerce, differing from each other by their microscopical features, the one consisting of flat tabular crystals (Fig. 41) , the other of fine needles (Fig. 42) . ”

“ From a large quantity of the substance to be examined, the coarse stones, etc., are removed by picking or sifting, and the prepared substance, or in cases where the impurities cannot be separated, the original substance, is treated with sulphuric acid; after it is decomposed, the acid is neutralized with calcium carbonate, and the nitrogen is determined in this mass.
In order to operate rapidly, it is best to use as little sulphuric acid as possible. If too much sulphuric acid is used, necessarily a large amount of calcium carbonate is essential to get it into proper condition for pulverizing. ”

“ A crystalline amalgam is formed with mercury, which may be distilled in hydrogen at 400° C, but which forms nitride when heated in nitrogen. Heated to redness with potassium or sodium chloride, calcium sets the metal free. Water acts on calcium only very slowly, with the evolution of hydrogen. In liquefied ammonia at-40° C. calcium ammonia is formed—a reddish-brown solid. ”

“ In a manufacturing plant the last two reactions take place in one process. Sodium sulphate, coal, and powdered limestone are heated together to a rather high temperature. The coal reduces the sulphate to sulphide, which in turn reacts upon the calcium carbonate. Some limestone is decomposed by the heat, forming calcium oxide. When treated with water the calcium oxide is changed into hydroxide, and this prevents the water from decomposing the insoluble calcium sulphide. ”

“ And calcium is present everywhere in nature! Even the purest mineral of potassium, sylvite (the salt, potassium chloride) , contains so much calcium impurity that the RADIOGENIC daughter calcium, produced by the decay of potassium in geologic time, is negligible in comparison. We can say that the bottom of this potassium-40 hourglass has been stuffed with so much sand from the very beginning that the few grains that fall through the waist are lost in the overall mass. This demonstrates that schemes involving the decay of a relatively rare nuclide into a relatively common one are not usable. ”

“ Oxalate of calcium falls as a precipitate, and soda remains in solution. This soda is boiled down, and again made use of with fresh sawdust. This recovery of alkali is also practised with the potassium salt which filters through in the last stage. (6) The oxalate of calcium is now decomposed in leaden vessels with sulphuric acid. Sulphate of calcium is precipitated, and oxalic acid is in solution, which is now evaporated, and the acid separates in crystals, which now need only to be recrystallised to make them quite pure, and fit the acid for all the purposes for which it is employed. ”

“ The Claus-Chance process, as it is called, comprises the following operations. The wet alkali-waste as it comes from the lixiviating vats, is transferred into upright iron cylinders in which it is systematically treated with lime-kiln gases until the whole of the calcium sulphide has been converted into calcium carbonate, the carbon dioxide of the lime-kiln gases being entirely exhausted. The sulphur issues as sulphuretted hydrogen, mixed with the nitrogen of the air. ”

“ Oxalic acid (or an oxalate) , when heated, in the dry state, with oil of vitriol in excess, is converted into carbonate anhydride and carbonic oxide; the former produces a white precipitate with lime water, and the latter, when kindled, burns with a faint blue flame. Of the above tests, solution of sulphate of calcium (vide No. 3) is the most delicate and characteristic.—5. It is distinguished from Epsom salt by its acid reaction, its solubility in rectified spirit, its complete dissipation by heat, and by emitting a slight crackling noise during its solution in water. ”

“ When sulphuric acid is used to precipitate the sulphur, sulphate of lime is formed and cannot be separated from the precipitated sulphur by the ordinary process of washing, that salt being insoluble in water; for this reason muriatic acid should be used, as the salt thus formed, the muriate of lime or chloride of calcium is perfectly soluble and can be readily separated from the sulphur by washing. ”

“ This has resulted from the oxidation of the sulphur to sulphuric acid by atmospheric agency, the acid in turn attacking the lime carbonate, and forming sulphate (gypsum) . The most plausible supposition as to the origin of the sulphur-seams would appear to be that the lakes received streams of water containing calcium sulphide in solution, this calcium sulphide probably resulting from a reduction of the masses of calcium sulphate (gypsum) by the action of volcanic heat. ”

“ It will be noticed that in the earlier stages the quantity of sulphur impurities is actually increased between the purifiers—in fact, the greater amount of sulphiding procures the ready removal of the carbon disulphide,—but it is the carbon dioxide in the gas that is the disturbing element, inasmuch as it decomposes the combinations of sulphur and calcium ”

“ Potassium is a constitutent of both animal and vegetable food; it occurs in considerable quantity in milk, and in the juice that permeates animal flesh; and most inland plants contain it. We derive the calcium of our system from flesh, bones, eggs, milk, etc. (all of which contain salts of lime) ; most vegetables also contain lime-salts; and another source of our calcium is common water, which usually contains both bicarbonate and sulphate of lime. Magnesium in small quantity is generally found in those foods that contain calcium. Iron is a constituent of blood found in meat ”

“ The human body contains a large store of phosphates which are excreted in the urine in combination with sodium and potassium—​and yet these do not draw the calcium from the blood, brain and bones! To be blunt, Nascher’s theory is absurd. The calcium in its various deposits in the body is already combined with phosphoric acid. Why should the phosphorus introduced take calcium from the phosphate radical with which it is already in combination? Nascher asserts that the phosphorus which is introduced as amorphous phosphorus is excreted as amorphous phosphate of lime within twenty-four hours. ”

“ To sum up, we see that, whether from food or from sea-water, calcium sulphate will tend to pass but little into solution in the albuminoid substances of the body: calcium carbonate will enter more freely, but a considerable part of it will tend to remain in solution: while calcium phosphate will pass into solution in considerable amount, but will be almost wholly precipitated again, as the albumin becomes broken down in the normal process of metabolism. ”

“ A sulphurous acid solution is made to circulate over the bones in a series of closed tanks, the solution being continually enriched with sulphurous acid from a cylinder of the liquefied gas. The resulting liquor, containing an acid calcium phosphate and calcium bisulphite, is heated by steam in a leaden digestor, when the excess of sulphurous acid is liberated and passes back to the tanks, while neutral calcium phosphate and sulphite are precipitated. ”

“ It dissolves readily in water, the solution having an acid reaction. The artificial manure known as “superphosphate of lime” consists of this salt and calcium sulphate, and is obtained by treating ground bones, coprolites, &c., with sulphuric acid. The di-calcium salt, Ca2H2 (PO4) 2, occurs in a concretionary form in the ureters and cloaca of the sturgeon, and also in guano. It is obtained as rhombic plates by mixing dilute solutions of calcium chloride and sodium phosphate, and passing carbon dioxide into the liquid. ”

“ When pure, calcium is not acted upon at ordinary temperatures by chlorine, though at 100° C. the action is decided. But if the metal contains nitride, chlorine attacks it at the ordinary temperature. At 300° C. calcium ignites and burns brilliantly in oxygen. Gently warmed in air, it burns with brilliant scintillations. It combines with sulphur, with incandescence, at 400° C. At a red heat it unites actively with lampblack, giving a carbide, CaC2. It gives some brittle alloys with magnesium, zinc, and nickel. ”

“ A mixture of pulverised chrome ore and chloride of potassium is exposed to a full red heat, on the hearth of a reverberatory furnace, with occasional stirring for some time, when steam at a very elevated temperature is made to act on it until the conversion is complete, known by assaying a portion of the mass; the chromate is then dissolved out of the residuum, as before. Common salt or hydrate of calcium may be substituted for chloride of potassium, when the chromates of sodium or calcium are respectively produced. ”