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for an hour or two, when the excess of the chloride of platinum will attract moisture from the air and afford an opportunity for the chloride of platinum and soda to crystallize regularly. For the most perfect success in very minute quantities of soda too great an excess of chloride of platinum should be avoided. Those engaged in mineral analysis, who will employ this means of detecting the presence of the alkali, will find it of great assistance in facilitating their labors, especially when directed to very minute accuracy in their results, for I have reason to believe it rare to find in minerals any one of the alkalies perfectly free from one of the others.

42. When the chloride of lithium is present it interferes materially with this method of detecting small amounts of soda; for, owing to its very deliquescent nature, it abstracts moisture from the air, and dissolves the double chloride of sodium and platinum, or prevents altogether its formation into recognizable crystals. These investigations have not added any thing to what is already known concerning the detection of lithia mixed with soda and potash; the plan invariably adopted is to treat the mixed chlorides with a solution of alcohol and ether, and examine the part dissolved by the blowpipe. Details as to the manner of using the alcohol and ether solution are given under the next head.

SEPARATION OF THE ALKALIES FROM EACH OTHER.

43. Under this head I have nothing to add to what is already known on the subject. It may be well, however, to mention the manner in which Rammelsberg's method of separating lithia has been employed, as it has not yet been fairly tested in this country. His method, it is well known, is based on the solubility of the chloride of lithium in a mixture of equal parts of absolute alcohol and ether, neither of the other chlorides being dissolved by this menstruum. A number of experiments were made on known quantities of the alkalies, and the results of some of them are as follows:

(a) Five hundred milligrammes of chloride of potassium treated with the mixture of ether and alcohol, ten grammes of the latter being used, yielded only three tenths of a milligramme to the liquid.

(b) Five hundred milligrammes of chloride of sodium treated in the same way yielded one half of a milligramme to the liquid.

(c) A mixture of chlorides of potassium, sodium, and lithium, in which the latter constituted two per cent. of the mass, was acted on by the ether and alcohol, filtered and evaporated to dryness; the residue was equal to 2.53 per cent. The quantity used was Cl K and Cl Na each 200 milligrammes, Cl Li 0.8 milligramme.

(d) A similar mixture containing 18.10 per cent. of chloride of lithium furnished a residue of 17.65 per cent.

(e) A similar mixture containing 67.20 per cent. of chloride of lithium gave a residue of 68.40.

44. By these results it may be seen that this method of separating lithia from the other alkalies may be perfectly relied on. It only remains to detail the precautions to be taken in order to insure accurate results.

45. The solution of alcohol and ether must be made of absolute alcohol mixed with its volume of pure ether. The chlorides must be dried thoroughly at 212° or a little above; if they have at any time been heated much higher, a drop or two of hydrochloric acid must be added to the chlorides, that are subsequently dried at the temperature just mentioned. The desiccation is best carried on in a small-sized capsule. To the dry mass a small quantity of the mixture of alcohol and ether is added and stirred with a small glass rod; the chlorides soon disintegrate; the capsule and its contents are placed on a glass plate and covered with a small bell-glass (a common tumbler answers the purpose very well, especially if the edge be ground); this is left to digest for twenty-four hours, and then thrown on a filter and washed with the alcohol-ether solution; the chlorides of sodium and potassium remain on the filter. These last can be dissolved off the filter by means of water, and separated in the ordinary way.

46. The alcohol-ether solution of chloride of lithium is evaporated to dryness, converted into sulphate, and weighed. The results thus obtained far exceed in accuracy those of any other method for separating lithia. The indirect method, by ascertaining the quantity of sulphuric acid contained in the mixed sulphates, is the next best, but like all indirect methods of analysis should never be employed except when it is absolutely

necessary.

47. When the alkalies are presented in the form of chlorides before their quantity has been estimated in some other form it is best to proceed first to the separation of lithia, afterward weigh the chlorides not dissolved by the alcohol-ether, and lastly separate the potash-chloride from the soda-chloride, if both be present, by means of the bichloride of platinum. Experiments were made with a mixture of alcohol and chloroform, the results of which were not as satisfactory as those afforded by the alcohol-ether.

SUBSTITUTION OF CHLORIDE OF AMMONIUM FOR FLUORIDE OF CALCIUM, TO MIX WITH CARBONATE OF LIME TO DECOMPOSE THE SILICATES.

48. It was mentioned in the previous paper on this subject how carbonate of lime could be rendered as powerful in its decomposing agency on the silicates as caustic potash, the effect being due to the use of some flux, fluoride and chloride of calcium being used for that purpose. I have since tested more carefully the merits of the chloride of calcium, and for various reasons prefer it to the exclusion of the fluoride. In the first place, it introduces chlorine instead of fluorine into the analysis; and secondly, the fusion is more easily detached from the crucible and dissolved by hydrochloric acid.

49. The manner of introducing the chloride of calcium into the mixture of mineral and carbonate of lime was a point of some little importance, as from the deliquescent nature of that compound it was inconvenient to weigh and mix it with the carbonate of lime and mineral. These difficulties are obviated by employing chloride of ammonium to form indirectly the chloride of calcium.

50. The process, which appears to leave hardly any thing to desire, is to take one part of the finely-pulverized mineral, five to six of carbonate of lime, and one half to three fourths of chloride of ammonium, mix them intimately in a glazed mortar, intro

The chloride of ammonium is best obtained in a pulverulent condition by dissolving some of the salt in hot water and evaporating rapidly; the greater portion of the chloride of ammonium will deposit itself in a pulverulent condition; the water is poured off, and the salt thrown on bibulous paper allowed to dry; the final desiccation being carried on in a water-bath, or in any other way with a corresponding temperature.

duce the mixture in a platinum crucible, heat to bright redness in a furnace from thirty to forty minutes.

*

51. There is no silicate which after having undergone this process is not easily dissolved by hydrochloric acid. For the action of the lime to have been complete it is not necessary that the mass should have settled down in a perfect fusion. The contents of the crucible are dissolved, and the analysis continued as pointed out in 19, 20, 21, etc.

52. This method insures the obtaining of every particle of the alkalies in the mineral examined, requiring no more. precaution than any good analyst is expected to take in the simplest of his processes, and not the least of the advantages is the ready method of separating all the other ingredients and the small accumulation of water arising from the little washing necessary.

A MORE SPEEDY METHOD OF SEPARATING THE ALKALIES DIRECTLY from the LIME FUSION FOR BOTH QUALITATIVE AND QUANTITATIVE DETERMINATION.

53. As soon as the fusion with carbonate of lime and sal ammoniac gave evidence of the mineral being so thoroughly attacked, the question naturally arose as to the condition the alkalies were in after the fusion, and the possibility of dissolving them out by the agency of water alone, at least for the purpose of qualitative determination. Experiments directed to this object soon made it evident that the alkalies might be obtained from any silicate without resorting to the use of acid as a solvent for the fusion.

54. The mass as it comes from the crucible is placed in a capsule with water, and then heated in a sand-bath or over a lamp for two or three hours, renewing the water from time to time as it evaporates. The mass disintegrates very shortly after being placed in the water. The contents of the capsule are next thrown on a filter, and the water passes through containing the chloride of the alkalies, a little chloride of calcium and caustic lime. All else that the mineral may have contained

* An ordinary portable furnace with a conical sheet-iron cap from two to three feet high answers the purpose perfectly well, all the requisite heat being afforded by it.

remains on the filter, except baryta and strontia, if they be present in the mineral; but as these oxides are of rare occurrence in silicates no allusion will be made to them here.

55. To the filtrate add carbonate of ammonia, and boil for some time, when all the lime will be precipitated as carbonate; add a few drops of a solution of carbonate of ammonia to the hot solution, to be sure that all the lime is precipitated. Should this be the case, filter; the filtrate will contain the chlorides of the alkalies and chloride of ammonium. It is evaporated to dryness over a water-bath in a small platinum capsule; the capsule is carefully heated to expel the sal ammoniac, and finally warmed up to 700 or 800° F. It is then weighted with its contents, and the chlorides, if mixed, separated in the way mentioned (45 and 46). The amount of sal ammoniac to be expelled is quite small, not equaling the weight of mineral originally employed.

56. Nothing in analysis can be simpler or more speedy than this process. Its constant accuracy still lacked some little to render it perfect, as usually an amount of alkali remains behind, represented by from two tenths to one per cent. of the mineral used; certainly a small amount, but still too much to be omitted in an accurate analysis. This also must be arrived at, and it can be accomplished in the following manner.

57. After the fused mass has been treated with water filtered and washed as in 54, the filter and its contents are dried; the latter are detached from the filter and rubbed up in a glazed mortar with an amount of sal ammoniac equal to one half the weight of the mineral, and reheated in a platinum crucible exactly as in the first instance, treated with water, thrown on a filter and washed, the filtrate added to that from the first fusion, the whole treated with carbonate of ammonia, and completed as in 55.

58. This second fusion complicates the method but little, as the residue on the filter readily dries in a water-bath into a powder that is easily detached from the filter, and the small portion adhering to the latter may be disregarded, as the alkalies remaining rarely exceed more than one five-hundredth of the whole mass, and in most instances not more than one thousandth. In many analyses made one fusion sufficed for the entire extraction of the alkalies; but as a few tenths would

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