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Previous Next The best candle and soap tips online! TECHNICAL TREATISE ON SOAP AND CANDLES. SOAP ANALYSIS. 351' but a uniform and thorough saponification is obtained at the instant that the heat and pressure arrive at the required degree, be the time long or short; if this degree is reached in five minutes, the soap is made. The inventors use from 30 to 33 lbs. of carbonate of soda at —48°, and 100 lbs. water to 100 lbs. of lard, tallow, or oil; 27 lbs. of carbonate will make a neutral soap for soft water. The product obtained is 200 lbs. of soap for every 100 lbs. of grease. Any kind of soap can be made by this process; soft soap is prepared with the same rapidity as any other, and is much more perfect and requires a less quantity of potash than by the open kettle process; four lbs. of potash being required for one barrel. To conclude, we would state that the advantages claimed for this process arc:— 1. The rapidity of manufacture. 2. The improvement in quality. 3. The increased quantity. 4. Economy in labor. 5. Saving of fuel. 6. The use of cheaper material. 7. The saponification of all the grease. 8. The uniform certainty of the results. 9. The saving of the valuable property of glycerine which greatly improves the quality of the soap. 10. The ability to use alkaline salts instead of caustic lye, obviating the necessity of using chloride of sodium, which is required by the common process, in order to get rid of the waste lye. Professor Dussauce examined some specimens of soap made by this process, and found them perfectly neutral, and entirely saponified, without a trace of carbonated alkali, and not containing as much water as soap made by the ordinary process. SECTION XVI. SOAP ANALYSIS. THERE are few articles of industry or commerce that are subject to so much falsification as soap, and it is partly because the public ignorantly wish a cheap one, hence there is always a desire to find a suitable and often an unsuitable substitute with which to adulterate it, to enhance the profits of unprincipled makers. There are many methods of analyzing and appraising soaps, but they are not so easy or simple that every one can perform them with the necessary accuracy. Soaps differ according to their value in alkali and to their organic ingredients, i. e., fat and rosin. Thus in the valuation of soap we have to consider: 1st. The contents of water; 2d. The proportion of sebacic acids to the alkali; 3d. The nature of the alkali and of the sebacic acid ; 4th. The intentional or unintentional admixture of foreign substances. Although the amount of water in a hard soap appears easily determined, it is nevertheless a somewhat difficult matter. This is easily seen when we know that each part of a cake or bar of soap contains a different amount, the outer part being denser than the centre, so a sample for testing should be a mixture of all parts to make an average. The sample obtained is to be scraped fine, the different parts uniformly mixed, and from this the quantity to be investigated weighed off; both operations, of mixing and weighing, must be carried out quickly so that the soap can neither absorb nor lose water. The sample, saj* about 10 grammes scraped soap, is placed in a small porcelain saucer, weighed, and placed over a water-bath and heated until the soap no longer loses in weight. At first the soap is left entirely untouched, and 352 TECHNICAL TREATISE OS SOAP AND CANDLES. SOAP ANALYSIS. 353 only when it has passed from the liquid into the pasty state the lumps are pressed with a glass epatula which has previously been weighed. If the two last weighings correspond, the soap is removed and weighed, and the loss is the weight of the water contained in the soap. Determination of the Amount of Alkali.—For this purpose it is well to use the dry soap left by the determination of the amount of water. This is placed in a glass flask, the porcelain saucer and glass spatula are repeatedly washed off in strong alcohol, putting all the liquid of the rinsing operation into the flask, then add from 50 to 60 cubic centimetres (1.69 to 2.03 fl. ozs.) of the strongest alcohol, the whole heated in a water-bath putting the stopper loosely on. The soap is dissolved, allowed to precipitate, and to cool off. The liquid, having cleared off perfectly, is decanted carefully into another larger flask. Pour over the residue some alcohol, let it settle, and operate as in the first case. The residue is then placed upon a filter and completely washed out with alcohol. The residue left on the filter consists principally of carbonate and sulphate of alkalies, carWnate of lime, and other mechanical admixtures. The residue is dissolved on the filter and with distilled water, washed out, when test the carbonate of alkali in the filtration, by alkalimetry, as also the sulphuric acid present, by chloride of barium in the liquid soured with muriatic acid. The sulphate of barium is placed upon a filter, washed out with distilled water, dried, calcined, and weighed. We calculate thus the sulphuric acid present, respectively, in the sulphate of potash and the sulphate of soda: 116.5 parts sulphate of barium correspond to 40 parts of anhydrous sulphuric acid, 87.11 parts anhydrous sulphate of potash and 71 pares anhydrous sulphate of soda. The liquid filtered off from the sulphate of barium is mixed for assaying the surplus addition of barium first with ammonia, then with carbonate of ammonia, filtered and washed out. The filtered liquid is evaporated in a small porcelain saucer until dry, and the muriate of ammonia ejected by calcination. The saucer is now placed upon a sensitive scale and balanced, emptying its contents without Previous Next
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