Towler, John. The Silver Sunbeam. Joseph H. Ladd, New York: 1864. Electronic edition prepared from facsimile edition of Morgan and Morgan, Inc., Hastings-on-Hudson, New York. Second printing, Feb. 1974. ISBN 871000-005-9
|Lithium: Symbol, Li.||Combining Proportion, 6 5/10|
|Barium.--Symbol, Ba.||Combining Proportion, 68 5/10, Specific Gravity, 4.|
|Calcium.--Symbol, Ca.||Combining Proportion, 20.|
|Potassium.--Symbol K.||Combining Proportion, 39.|
|Sodium.--Symbol, Na.||Combining Proportion, 23. Specific Gravity, 0.97.|
|Ammonium.--Symbol nh4=Am.||Combining Proportion, 18.|
|Cadmium.--Symbol, Cd.||Combining Proportion, 56. Specific Gravity, 8.6.|
Take one part of phosphorus, twenty-four parts of iodine, and forty of warm water; mix them intimately in a Wedgwood mortar by means of the pestle. The color of the fluid is at first dark brown, but becomes transparent as soon as the decompositions are effectuated. The heat of a water-bath and friction will soon complete the action. By this operation, iodine and phosphorus combine, so as to form iodide of phosphorus, which becomes resolved into hydriodic acid and phosphoric acid by the decomposition of the water. A little free iodine added to the transparent solution prevents the formation of phosphorous acid.
To the transparent solution above obtained, by decantation from any remaining phosphorus, add, in the first place, carbonate of baryta as long as effervescence ensues, and afterward a little water of baryta, so that the mixture becomes slightly alkaline. By this decomposition phosphate of baryta is formed from the phosphoric acid and the carbonate of baryta; and from the hydriodic acid, and the carbonate of baryta, iodide of barium is the resulting formation; and carbonic acid is liberated as gas. The iodide of barium, being soluble, is separated from the insoluble phosphate by filtration. A current of carbonic acid is now passed through the filtrate, in order to combine with any remaining solution of baryta, and the mixture is again filtered.
This salt is obtained precisely in the same way as the preceding substituting only milk of lime for the barytic salt. Both these salts crystallize, when slowly evaporated; they are, too, both deliquescent. Froth either iodide of barium or iodide of calcium the alkaline iodides are easily formed.
Add two ounces of carbonate of lithia to the iodide of either barium or calcium solutions produced from seven ounces of iodine by the preceding manipulation. The carbonate is previously levigated in water to an impalpable consistency. The mixture is frequently stirred during the twenty-four hours it is allowed to stand, in order to effect the complete precipitation of baryta or lime. The solution of iodide of lithium is now separated by filtration from the insoluble carbonate of baryta or lime. If the iodide of barium or of lime has not been thoroughly decomposed, add a cold solution of carbonate of lithia as long as any precipitate is formed.
Digest a hot solution of sulphate of potassa in a solution of iodide of calcium in the proportion of their equivalents for six or eight hours. Double decomposition ensues, the sulphuric acid and oxygen of the potassa combine with the lime to form sulphate of lime, whilst the iodine and potassium enter into combination to form iodide of potassium. By filtration through cloth these two salts are separated. The liquid, containing probably still some iodide of calcium and solution of sulphate of lime, is evaporated and then treated with pure carbonate of potassa as long as any precipitate is produced. The insoluble lime is again separated, and the filtrate is evaporated to crystallization. The mother-liquor is afterward evaporated to dryness.
These two salts may be prepared in like manner, either from the iodide of barium or of calcium, by the substitution in one case of sulphate and carbonate of soda, and in the other of sulphate and carbonate of ammonia. The results are better with the iodide of barium, owing to the more perfect insolubility of the sulphate of baryta after decomposition. Both of these iodides, as well as that of potassium, may be obtained by the direct action of iodine on the caustic alkalies. In this way iodine is added to a solution of potassa, for instance, until the latter becomes slightly colored; the solution so obtained contains iodide of potassium and iodate of potash; it is evaporated to dryness, and then heated to redness, in order to convert the iodate of potash into iodide of potassium by driving off its oxygen. The fused mass is afterward dissolved and crystallized. Sulphuretted hydrogen is sometimes used to decompose the iodate.
Another method, similar to the first, consists in first obtaining either the iodide of iron or of zinc, by mixing iodine, water, and iron-filings, or iodine, water, and zinc-filings, together, and then heating the mixture until the combination is complete, which is indicated by its becoming colorless. The filtered solution is next decomposed completely by adding solution of carbonate of potassa as long as any precipitate takes place. The precipitate, which is either carbonate of iron or of zinc, is removed by filtration; and the filtrate is evaporated to crystallization.
This very important iodide is formed precisely in the same way as iodide of iron or of zinc, by gently heating a mixture of the filings of cadmium, water, and iodine, until the solution becomes colorless.
The iodides which are formed by the direct contact of the two elements are quite pure if the materials are pure; whereas, if the iodides arise from double decomposition, the combination may sometimes fail in accuracy, in which case carbonates and sulphates of foreign ingredients and iodates of the same base nay be found in such iodides; chlorides may be present, too, in the decomposing carbonates and sulphates, so that we may sometimes expect to find them with the other impurities.
No precipitate is produced in a pure iodide by solution of chloride of barium. If a precipitate results from the introduction of this test, one or all of the following acids are probably indicated: carbonic, iodic, and sulphuric. Other acids might be indicated, but not probably, because materials are not used in the preparation of the iodides containing the acids hinted at, as, for instance, oxalic, sulphurous, silicic, chromic, hydrofluoric, phosphoric, and boracic. Supposing, however, a precipitate is formed when the test is added, then a carbonate, iodate, or sulphate may be one or all present. The next test is to find out which or how many of the three are present. Add, therefore, nitric acid to the precipitate; if it becomes dissolved, there is no sulphate in the iodide. Carbonic acid or an alkaline carbonate added to lime-water produces a milkiness caused by the formation of the insoluble carbonate of lime; and an iodate in solution is recognized by the addition of chlorine-water, or citric, or tartaric acid, which liberates free iodine, afterward made manifest by solution of starch. The chlorides are tested for as follows: in a given quantity of the iodide precipitate with solution of nitrate of silver, until nothing more falls as sediment; dissolve this sediment in ammonia, and then add nitric acid; if a chloride is present, a white flocculent precipitate will be produced, which is chloride of silver.
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