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Previous Next The best candle and soap tips online! TECHNICAL TREATISE ON SOAP AND CANDLES. RECOVERY OF REFUSE FATS. 139 once brought into the tratle, or they are previously bleached. For draining off the water the emulsified oil stratum is either heated by the addition of culinary salt over an open fire (in case of a common kind of fat), or (for better sorts of fat) with indirect steam. This latter mode of heating is applied especially when the soap-waters originate from the scouring or boiling of silk, or from Turkey-red (Adrianople red) dyeing establishments; hence in greater part being the result of olive-oil soap. For bleaching purposes a solution of sulphuric acid mixed with chromate of potash is used. When separated and washed, the yet .warm sebacic acid3 of the lime soap are placed in the vats (with the emulsion stratum), and while being diligently stirred the bleaching liquid is added, and the mixing kept up for half an hour longer. After resting six hoars the bleached sebaeic acids are, in a great measure, separated; the green aqueous liquids being drawn off they are washed once or twice with warm water. After the wash water has been removed the oil emulsion ia drawn off. The clear fat mass is then at once drained of water. The emulsive stratum is mixed with 10 to 15 per cent, of canadol (a kind of benzole), whereby an immediate separation ensues, and the canadol is again separated by distillation. This treatment of the emulsified stratum with canadol takes place only after five or six bleaching operations, that is when sufficient material has accumulated to nil a distilling apparatus. The canadol regained can always be used again for renewed operations. In this manner the sebaeic acids recovered from the silk-scouring and Turkey-red dyeing establishments are of a light yellowish color, and possess but a faint odor. Yohl has not, we are sorry to state, communicated the results of his experiments, eo that a comparison between his and the usual method of operation is impossible. It is known, however, that chloride of alkalies cannot be completely removed from sebacic acids by washing with water. From this fact reason is found tor objections to Vohl's method. Vohl attempts to remedy this difficulty by the partial application of canadol. The wool-fat, as usually brought into the market, is a solid, tough, dirty, yellow-brownish mass, which is difficult to remove with the spade from the casks in winch it i? packed for transportation, It finds application in the manufacture of soaps, and in the fabrication of lubricators. For soap-rnaking it serves principally in the preparation of rosin soap; but soap-boilers do not much like to work it on account of its inferior yield, which is explained by its chemical composition. Fuller's-fat forms a thick oily mass, and is a much more valuable fat, as its price indicates, ?which is quoted at about double that of wool-fat. It likewise finds application chiefly in the fabrication of oila for lubricating and in the manufacturing of rosin soaps. These offal fats are never by themselves used for soaps; but always in combination with other fats, particularly palm oil or tallow, and especially with roain, saponified. By using these refuse fats for lubricating materials, it is considered that they are not neutral, but contain free sebacic acids. It is therefore almost always more desirable to use them for soap. Vohl in 1867 attempted to calculate the amount of soap used in the city of Cologne, and the loss of fat caused thereby, and reached the result, that that city* which at that time contained 120,000 inhabitants, lost annually by the soap used 1.200,000 pounds of fat. This calculation extends only to tbe soap consumed for private purposes. ^Establishments of industry, hospitals, and other public establishments are not considered in his calculation, so that the total loss in fat is really still higher. In consideration of the large amounts which this loss represents, and considering that the products of decomposition of the soap-water, which finds its way into gutters, culverts, etc., develop unwholesome miasma, Vohl proposed to collect the Boap-waters even in private residences, and to deliver the same to the respective manufactories for working them up. This proposition, however, will for a long time to come remain naught else but a well-meant desire, and we must regard it already as a great progress, when those who possess a great quantity of refuse and oflals containing an amount of useful materials, begin gradually to utilize them. 140 TECHNICAL TREATISE OS SOAP AND CANDLES. ADULTERATION OP THE FATTY BODIES. 141 SECTION V. THE ADULTERATION OP THE PATTY BODIES. FATS and oils are subject to adulteration and falsification, particularly those of great commercial value, and generally with fats and oils of lower prices. Uy exposure to the air they absorb oxygen and become rancid ; some oils dry into a kind of varnish, and are called drying oils; the fats are adulterated with foreign substances to increase their weight. We cannot here go into a general analysis of all these important materials, lut will examine such as are in common use and most liable to sophistication. OLIVE OIL. Olive oil for the manufacture of soaps is ordinarily adulterated with cole-seed oil, cotton-seed oil, and poppy oil. These mixtures ar« sometimes disguised by coloring them green with indigo, so as to create the impression that green olive oil is present. The adulteration with black poppy oil is the most frequent, not only on account of the cheapness of this oil, but also on account of its sweet taste, and its odor being but little pronounced. We shall see hereafter the process for detecting these falsifications. OIL OF SWEET ALMONDS. The oil of sweet almonds is principally falsified with poppy oil and with sesame oil. Several processes have been proposed for detecting this falsification. Oil of sweet almonda becomes cloudy at —20° C. (4° below Previous Next
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