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Previous Next The best candle and soap tips online! loss into a 100 cubic centimetre (3.38 fl. ozs.) measuring flask, rinsing the saucer with water, drj'ing it by warming,placing it again upon the scale, and by additional weights causing it to balance. The weights placed on after deducting the calculated sulphate of potash found in the sulphuric acid, show the alka lies present as chloride of potassium and chloride of sodium. We will designate this weight by A. To find herefrom the respective quantities of soda and potash, we determine the quantity of chloride in A, by dissolving the salt mixture to 100 cubic centimetres (3.38 fl. ozs.), then placing a. certain part of this solution (10 to 20 cubic centimetres = 0.338 to 0.676 fl. oz.) in a white porcelain saucer, adding a few drops of neutral chromate of potassa, and then from a T'-ff cubic centimetre graduated pipette so much standard nitrate of silver solution until the ensuing precipitate shows a reddish coloring. By determining the chloride, the data for con tinuing the calculation are given. We know now, 1, the weight A, and, 2, that of the chloride contained therein = C. If the two unknown quantities are designated chloride of potassa with x and chloride of sodium with y, there is x + y = A. I. The chloride of potassa contains the 0.47552 of its weight of chloride, the chloride of sodium the 0.60657 part of its weight of chloride. x parts chloride of potassa hence 0.47552 x parts chloride and x parts chloride of sodium hence 0.60657 y " " 0.47552 x + 0.60657 y = II. If we place of equation I. for x its value, to wit, x = A — y, and substitute it in the equation II., then we obtain: 0.47552 A + 0.13105 y = C, and herefrom C —0.47552 A 0.13105 0!60657_A—LC 0X3105 From the figures thus found for the chloride of potassa and the chloride of sodium, we calculate the potash and the soda according to the proportions. 23 354 TECHNICAL TREATISE ON SOAP AND CANDLES. SOAP ANALYSIS. 355 74.56 parts chloride of potassa are = 47.11 parts potash and 58.45 " chloride of sodium " = 31.00 "• soda. These salts do not form a constituting ingredient of the soap, they are an intentional ov accidental surplus present. The sulphuric acid is, in the first place, calculated as sulphate of potassium and a surplus as sulphate of sodium, the rest is carbonate of potassa or carbonate of soda. The alkaline chloride, and also the free caustic alkalies, are found in the alcoholic solution, and are determined in the following manner: This alcoholic solution is well and constantly shaken, with an accurately weighed quantity of bicarbonate of soda, or potash. By this process the caustic alkalies change into carbonates, which, as they are insoluble in alcohol, will precipitate to the bottom. Now we decant, rinse the residue with alcohol, and then place upon a filter, where it, is fully washed out with alcohol. The residue upon the filter, dissolved iu distilled water, determines in the iiltrations by means of standard nitric acid the carbonate of soda, and deducting from the quantity thus found, the applied bicarbonate of soda, the rest is that surplus carbonate of sodium, which was present in the soap. In the alcoholic soap solution now only remains for determination the chloride of potassa, as also the alkalies combined with the sebacic acids. For this purpose, the solution is divided into two equal parts. The one of these parts is analyzed by a measured quantity of standard nitric acid, which is wanned until the separated sebacic acid melts, separating them, after they congeal, melting them again in distilled water, and uniting the here obtained acidy liquids. The surplus of the acid is now titrated back, and finding now from the nitric acid neutralized by the alkalies, the alkalies present potash and soda. In the same liquid, after having been made somewhat alkaline by a few drops of carbonate of soda; and having colored it yellow, with neutral chromate of potassa, we determine by means of T'o- nitrate of silver, the value of chloride of potash. A more simple, although less accurate, yet in most cases amply sufficient method, by which to determine the value of free alkalies (caustic as well as carbonate) contained in soaps, consists in weighing a portion of the soap, dissolving the same in distilled water, and separating it with culinary salt, whicb has no earthy salts, gypsum, chloride of calcium, or chloride of magnesium, etc., or rock-salt. We must not warm it, so that the soap separates grainy, and it is then washed out upon a filter with a concentrated solution of pure chloride of sodium. In the filtered liquid, the alkalies are found dissolved. In order to determine the carbonate and the caustic alkali separately, the solution is mixed with chloride of barium, gathering the precipitate upon a filter, washing it out, and putting it into a beaker glass, wherein it is dissolved in a surplus of measured standard nitric acid, and the surplus of the latter is then analyzed by means of the staudard alkali. From the nitric acid used, the quantity of carbonate of potash or soda, or both together (specifically only the quantity of the carbonates) is ascertained. The liquid filtered off from the carbonate of barium, contains the caustic alkalies, which may then be determined by alkalimetry. In the testing of soda-soaps, as a rule no consideration need be taken as to their value in potash; but if this is nevertheless intended, one part of the liquid is to be concentrated and mixed with bichloride of platinum. If no yellow precipitate ensues then no potash is present. It yet remains to determine the relative quantities of potash and soda, which have really formed the soap. To this end, the other part of the alcoholic soap solution is to be analyzed. This is done by muriatic acid, separating the sebacic acid from the liquids, washing it well with water, and finally evaporating theacidy lye with the washing water in a porcelain saucer, until it becomes entirely dry. Here great care must be taken, so that no loss is experienced. The porcelain saucer, while yet a little warm, is placed on the scale and balanced; it is then removed, emptied, rinsed,and dried by warming, and again placed while yet a little warm upon the scale and again weighed. Thus the aggregate quantity of alkaline chlorides is obtained, from which the chloride of potassa found in the first test is deducted, and 356 Previous Next
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