THE A N A L Y S T . ON THE ESTIUATION OF OLEINE, &c., IN FATS, BY DR. MUTER, F.C.S. IT is a principle well-established and laid down in most works on chemistry, that oleine may be separated from stearine and palmatine by taking advantage of the solubility of oleate of lead in ether, but the best methods of carrying out the separation are not as a rule given. I believe that the ordinary idea is to saponify with oxide of lead and water, dissolve in ether, remove the lead by sulphurctted hydrogen, and weigh the oleic acid, but in practice this is a very undesirable method.A much better way is to follow somewhat closely a commercial process, known in Holland, of separating the oleic acid from the lead by hydrochloric acid in the presence of ether, but there are several important precaution3 necesaary to be attended t o so that accurate results may be obtained.In the course of my experience in the analysis of fats, I have noticed several points, and I propose to give them in as short a form as possible, together with a detail of what I have found to be the most simple and accurate processes. The first important matter is to ensure the formation of a perfectly neutral plumbic oleate, Pb 2 c,,, H33, O,, as the slightest quantity of basic oleate will render the analysis inaccurate, owing to its much less degree of solubility in ether.To attempt this by the ordinary method of saponification with plumbic oxide is quite hopeless, but it may be readily attained as follows :-A small quantity (not more than 1 * 5 grammes) of the fat is saponified by alcoholic potash and then well diluted with Foiling water.The solution is carefully treated vith acetic acid till feebly acid, and then worked back with dilute potash till just neutral. This can be done without the use of test paper, by adding the acid to the soap solution, at the boiling point, until a decided pemanent turbidity is produced, and then dropping in the potash vith constant stirring, until the liquid jmt clears again.The clear solution is then precipitated by plumbic acetate in slight excess, and stirred until the precipitated soap settles thoroughly. The supernatant liquor is poured off, and the soap once washed by boiling with a large volume of water and decanting. Pb 2, (318, Hs, 0, . . . . . . . . . Plumbic Oleato.Pb 2, (316, H31, 02 . . . . . . . . . Plumbic Palmitate. Pb 2, CIS, &, 0, . . . . . . . . . Plumbic Stearate. By this process we obtain the perfectly neutral lead salts, coritaining :- The first being readily soluble in ether, and the two latter quite insoluble. The soap is scraped from the basin with a platiuum spatula and transferred to a flask of 100 C.C. capacity.The basin is rinsed into the flask with absolute ether, and then the flask is filled up with the same solvent, corked, shaken at intervals for some hours, and finally set to subside. The whole is then filtered through white filter paper, and the precipitate washed with ether till the washings cease to blacken with ammonium hydrosulphide. The filtrate and washings (which should not exceed 200 c.c.) contain the plumbic oleate, whilst the palmitate ctud stearate remain an tho filter.74 THE ANALYST.I have proved by many experiments that the solution really does contain pure plumbic olcate, of which I will, however, only notice the one in which I got the greatest divergence from t h e o q ; 40 C.C. of the ether solution evaporated yielded 1.162 of residue; another 40 C.C.mere then shaken up with hydrochloric acid, mixed with alcohol, and the plumbic chloride formed collected, dried, and weighed on a tared filter. The weight of Pb C1, = ~424, equal to *340 C1,plumbic oxide, thus showing 29.26 per cent. of oxide of lead-theory requiring 29 per cent. Having thus got a solution of the pure neutral lead soap in ether, it is transferred to a long graduated tube of 250 c.c., graduated from the bottom upwards, and furnished with a well ground stopper and a stop-cock, which is placed at 50 C.C.from the bottom.* About 20 C.C. of a mixture of one part hydrochloric acid and two parts water is then added, the tube is stoppered, well shaken, and set to subside, when a clear solution of oleic acid remains, the plumbic chloride sinking to the bottom.Vhen sufficiently settled, a fixed portion of the ethereal solution is run off through the stopcock into a tared platinum dish, evaporated and dried a t 21Z0, and the oleic acid is weighed and calculated t o the whole bulk. To make sure, it is well to run off two different quantities and weigh them, so checking the one by the 0ther.t I f it is desired to estimate the stearic and palmitic acids together, the residue should be filtered and the soap remaining on the filter detached and heated for some time (with constant stirring) with dilute hydrochloric acid, which will liberate the acids so that they may be collected and weighed in the usual manner.The filter paper is also to be turned and the ash treated with a drop or two of snlphuric acid, and any lead remaining on the paper weighed as sulphate, 303 parts Pb S 0, equalling 568 parts stearic acid.For those who may not wish t o go t o the expense of the special tubes, and who do not grudge a little extra trouble, the oleic acid may be estimated in the ethereal solution of plumbic oleate, by simply making it up t o a knowc bulk and taking a fixed portion in a tared platinum dish.This may then be evaporated, dried at 212, and the plumbic oleate weighed. To cnsurc absolute accuracy, however, (lest by imperfect manipulation trace of basic oleate be present) it is necessary, in this case, t o ignite the weighed residue, and again weigh as Pb 4- Pb 0. This residue is treated with acetic acid to take up the Pb 0, and again weighed, and the residual Pb calculated to Pb 0, By deducting the weight of plumbic oxide thus obtained from the total plumbic oleate, and allowing for the hjdrogen displaced, we get the oleic acid.I prefer, of course, in all cases to use the tubes, 8s with them the process is much more rapid and fairly accurate. I give the following selected analysis as showing the extreme divcrgences from truth that I hare obtained a t various times.Oleic Acid ... ... ... ... 40.4 Stearic and Palmitic Acids ... ... ... 47.5 A sample of butter, yielding 88.5 insoluble acids gave- 8 7 9 total. * These tubes are especially made for me by JIRIem-s. Jackson, Barbicm, E.C., aiid can be obtained t The more fluid drawn off for each weighing of course the less the possible error. f'rom them.THE AKALYST.75 Another sample of butter, yielding 87.1 insoluble acids gave- Oleic Acid ... ... ... . a > 34.8 Stearic and Palmitic Acids.. ... ... 52-1 . 86.9 total. h sample of lard, yielding 95 per cent. insoluble acids gave- Oleic Acid ... ... ... ..* 47.5 Stearic and Palmitic Aci rls... ... .., 4 7 4 94.9 total, Two different experiments for oleic acid only in tho same sa nple of fats- 1st experiment. 2nd experiment. 43.2 ... ... ... 43-8 46.8 .,. ... ... 46.6 52.7 ... ... ... 53.0 48.0 ..9 ... ... 49.0 The worst experiment was done at an early stage of the investigation and represents an amount of error not likely t o occur after practice. I am now engaged in applying the process to the analysis of lard, in the hope of establishing a standard for calculating its adulteration by other fats, but as yet 1: fear its relative proportions of fatty acids are too variable for much success in this direction,