It is distin cheesy smell and taste, and becomes readily rancid. guished from most fats by its ready solubility in alcohol. To obtain the acid, the fat is converted into soap by boiling with an alkali, and the soap decomposed by a mineral acid. The fatty acid mixture obtained is subjected to strong pressure to remove the liquid acid (probably oleic acid), and the pressed cocoic acid is further purified by a second saponification. The soap is repeatedly dissolved in water and separated by the addition of common salt, by which means it is rendered colourless. It is then decomposed by tartaric acid, and the fatty acid crystallized from alcohol till its melting point becomes constant. It is snow-white, inodorous, and melts at 95°, congealing into a mass like wax. When melted with oxide of lead, it loses 4 eq. water. With the alkalies it forms salts which are soaps, like the salts of the more common oily acids. The cocoate of oxide of ethule is obtained by passing hydrochloric acid gas into a solution of cocoic acid in alcohol, and adding water. It is a colourless mobile liquid, having a pleasant smell of apples. The cocoate of silver. is white and insoluble. SERICIC ACID. Syn. Myristic Acid. Discovered by Playfair. acid in the salts of baryta and potash, C2H27O3. crystallized acid, C28H27O3 + HO. (Playfair.) Formula of the This acid exists in combination with oxide of glycerule in the butter of nutmegs, which are the fruit of Myristica moschata. This butter is soluble in 4 parts of hot alcohol, and the solution deposits on cooling silky crystals of sericate of oxide of glycerule (sericine or myristine). From this purified fat the acid is obtained by the usual process for oily acids, as described for the preceding acid. It is purified by repeated crystallization from alcohol or ether. It forms brilliant white scales of a silky lustre (hence its name), fusible about 120°, and congealing into a crystalline mass. It is soluble in alcohol and ether, and is decomposed by nitric acid, and by heat. The salts which sericic acid forms with alkalies are distinguished from other soaps by not forming viscid solutions when concentrated, and by not becoming turbid when diluted, as ordinary soaps do. 0.864. Formula, 2 Se + 5 - Sericate of oxide of glycerule, or sericine, exists in the butter of nutmegs. It is purified by washing with alcohol, pressure, and solution in hot ether, from which it crystallizes on cooling. According to Playfair, its formula is C118H113015=4(C28H27O3) + CH2O. This would give for the oxide of glycerule in this fat the formula C6H5O. Whereas, according to Pelouze, oxide of glycerule is CH7O5. But it is not impossible, as Liebig has suggested, that there may be more than one oxide of glycerule. According to Lecanu, oxide of glycerule is CHO4; and it will be seen that these three formulæ only differ in the proportion of water. Liebig supposes that these different varieties of glycerine may require different quantities of acid for neutralization, just as some acids are monobasic, others polybasic. He considers stearine a compound of 2 at. stearic acid, 1 at. oxide of glycerule — C¿H,O and 2 at. water; while in sericine, the oxide of glycerule C6H5O3, which contains 2 at. of water less, is combined with 2 at. of acid more, 4 at. in all. It has also been supposed by Liebig that oxide of glycerule may be C,H2O, in which case the formula of sericine may be Se+ GlyO, or possibly 2(Se, GlyO) + 2(Se,HO). Like all compounds of glycerule, sericine, when distilled, yields the pungent vapour of the substance to be afterwards mentioned, which is called by Berzelius Acroleine. These views are highly ingenious, and promise to throw much light on the constitution of the oils and oily acids; but they require extensive and minute researches to establish them. This subject will be again considered when we come to give a general sketch of these important compounds. 2 Sericic acid, when heated with potash and a little water, forms a beautiful white soap, which crystallizes out of alcohol. This, as well as the sericate of baryta, is composed according to the general formula Se, MO. But it Sericate of silver appears to contain water, a rare occurrence in a salt of silver. If so, its formula is 2(Se,AgO) + HO. is more probably Se, AgO. Sericate of lead, like some other salts of lead, when prepared from the acetate, contains acetate of lead. Its formula is C116H111 01597PbO4(C28H27O3,PbO) + (Â3PbO). Playfair, to whom we are indebted for the above and other facts, remarks that sericic acid is not far removed in composition from œnanthic acid. In fact, 2 at. œnanthic acid=C28H2604 represent 1 at. sericic acid in which 1 eq. of hydrogen has been replaced by 1 eq. of oxygen. It is thus related to œnanthic acid, as hyduret of benzule is to benzoic acid, at least as far as the formulæ are concerned; but no conversion of the one into the other has been observed. Besides sericine, the butter of nutmegs contains a reddish fat and an aromatic volatile oil. The reddish fat, when distilled, yields, among other products, a black fat, soluble in alcohol and ether. These products have not been further examined. PALMITIC ACID. Formula Formula of the acid in the salt of silver, C2H3103. of the hydrated acid, C ̧1⁄2H ̧1O3 + HO. (Fremy, Stenhouse.) Discovered by Fremy in palm oil. To obtain it, the oil is saponified by a caustic alkali, and the soap decomposed by an acid. The oily acid which separates contains some oleic acid, which is removed by solution in alcohol, and by pressure. In appearance the palmitic acid resembles margaric acid, forming pearly scales. It has also the same melting point, namely 140°. It is saponified by digestion with the carbonated alkalies. It is partly decomposed by distillation. By chlorine it is acted on in a way similar to valerianic acid, yielding a variety of acid oils, in which hydrogen is more or less completely replaced by chlorine, and which retain their chlorine in combining with alkalies. Palmitine, or palmitate of oxide of glycerule, is the principal solid ingredient of the palm oil or butter. It is purified by pressure, washing with hot alcohol, and finally crystallization from hot ether. It is white and crystalline, very sparingly soluble in hot alcohol, but very soluble in hot ether. It melts at 118°, and congeals to a mass like wax, which is friable. According to Stenhouse, its formula is C35H3O4, which would indicate a compound of 1 at. anhydrous palmitic acid, C2H31O3, united to C2H2O; which is the same formula for glycerine as one of those mentioned under the preceding acid as suggested by Liebig. This is possibly derived from ordinary glycerine, CH,O,; for CH,0,- 3HO= CH2O2 = 2(C2H2O). Like all the compounds of glycerule, palmitine when distilled yields the penetrating vapours of acro leine. CETULIC ACID. Syn. Aethalic Acid. Composition and formula identical with those of palmitic acid, from which, however, it differs in properties. (Dumas and Stass.) Formed by the action of fused potash on ethal (hydrated oxide of cetule). Symbol, Cet. The formula of ethal is C2H3402; that of cetulic acid is C32H3204 The latter is therefore produced from the former, 2 eq. of hydrogen being replaced by 2 eq. oxygen. The oxygen is derived from the water of the hydrate of potash, so that 4 eq. of hydrogen are set free in the process, 2 from this source, and 2 from the ethal. To prepare the acid, 1 part of ethal is heated with 6 parts of a mixture of fused potash and quicklime in equal proportions, to the temperature of about 425°. Hydrogen is set free, and cetulate of potash is formed. This salt is converted, by means of chloride of barium, into cetulate of baryta, which is purified from ethal by digestion in ether. The cetulate of baryta is decomposed by diluted hydrochloric acid, when cetulic acid is obtained in the form of a fat, fusible at 130°, volatile, insoluble in water, soluble in alcohol and ether. Its salts have the general formula Cet, MO. They have been little studied. MARGARIC ACID. 68 Formula of the anhydrous acid, C34H33O3, or C68H66O6. Symb. Mr. Formula of the hydrated acid, C6sH66O6 +2HO. (Varrentrapp, Redtenbacher, Bromeis, Stenhouse.) Symbol, Mr,2HO. A bibasic acid? Discovered by Chevreul. Syn. Margarulic Acid. Margaric acid, one of the most widely distributed and most important of the oily acids, is found in combination with oxide of glycerule, (glycerine, sugar of oils,) in several species of animal and vegetable fats and oils, particularly in human fat, in goose fat, and in olive oil, being in these cases mixed or combined with oleate of oxide of glycerule. It is also produced by the action of heat on tallow (stearate of oxide of glycerule) and on stearic acid, and by the oxidation of stearic acid. The easiest method of obtaining pure margaric acid is to heat hydrated stearic acid with its own weight of nitric acid for some minutes. The fatty acid which separates on cooling is exposed to pressure to remove oleic acid, and purified by repeated crystallization in alcohol, till its melting point becomes constant. It may also be obtained by decomposing pure margarate of lead or of lime by a diluted mineral acid. Margaric acid has the aspect of a fat, fusible at 140°. Its solution in alcohol has an acid reaction. From ether or alcohol it crystallizes in pearly scales; hence its name. With bases it forms two series of salts: a. Neutral, the general formula of which is Mr + 2MO; b. Acid, the general formula of Margarate of Oxide of Ethule.-Mr,2AeO. (Varrentrapp.) Prepared by the action of hydrochloric acid gas on an alcoholic solution of margaric acid, and purified by washing with boiling water. It has the appearance of a fat, which melts at about 70°. The margarates of potash and soda are obtained pure by the following method, which we owe to Chevreul. The fat of man, or of the goose, or olive oil, is saponified by boiling with caustic potash or soda. The soaps obtained are decomposed by a mineral acid; and the fatty acid which separates, a mixture of margaric and oleic acids, is heated with 8 parts of water, and potash or soda added till a clear solution is obtained. This solution is then mixed with 50 times its volume of water, which causes the separation of acid margarate of the alkali in pearly scales. These are again dissolved in 8 parts of water, the solution again rendered clear by potash or soda, and again mixed with 50 volumes of water. This operation is repeated till the salt, when decomposed, yields an acid fusible at 140°. The salt is then free from oleate of KO HO potash or soda. The acid margarate of potash is Mr, Heated with as much more potash as it already contains, it yields the neutral salt, Mr,2KO, which is a regular soap, of a rather soft consistence, soluble both in water and alcohol, but which, when mixed with much water, yields free potash and the acid salt, the latter being insoluble. |