THE ANALYST. 247 ON BELFIELD’S TEST FOR BEEF-STEARINE I N LARD. BY OTTO HEHNER. UPON the form of the crystalline deposit obtained from an ether solution of lard is based the only method extant for the detection of beef-fat in lard. Pure lard, as a rule, gives, as is well-known, crystals which are flat, with chisel-shaped ends, some- times single, often bunched together, and radiating from a centre, while in presence of beef-fat the crystals form exceedingly thin needles, curved, united in the form of wheatsheaves or horsetails, with pointed ends. It has been shown by Mitchell and myself (ANALYST, vol. xxi., p. 328, and American Chem. SOC. Journal, vol. xix., 1897) that the “form of the beef-crystals is soleIy due to a larger proportion of stearic acid than can be obtained from pure lard by a single crystallization,” and that by recrystallizing the deposit the stearic acid accumulates to such an extent, even in deposits from pure flare lard of average composition, that the crystals become indistinguishable from those obtained from beef -f at.248 THE ANALYST.In the paper referred to a number of determinations of stearic acid in lards and other fats are given, showing that the highest percentage of stearic acid met with by us up to that date was 16. It was to be expected that in lards with a higher proportion of stearic acid the form of the crystals would more and more nearly approach to that associated with beef-fat. I have lately melted out in the laboratory from a piece of pig’s flare some lard which gave an iodine absorption of only 45.6, and containing, as the average of two satisfactorily agreeing determinations, no less than 24.91 per cent.of stearic acid. The crystals from this sample are indistinguish- able from those of lard largely admixed with beef-fat. In a second sample of flare- fat I found 20-75 per cent. of stearic acid; the ether-deposit from this sample also closely resembled that of beef-stiffened lard. A sample of mutton-fat contained 27.4 per cent. of stearic acid, and the crystals had all the appearance of beef- s tearine crystals. As, with the exception of the figures published by Mitchell and myself, no data as to the percentage of stearic acid in fats, based upon direct determination, are available, I think it worth while to place the above numbers on record. They should make analysts very cautious in placing reliance upon the form of the ether-deposits. When cotton-seed or other vegetable oil can be traced, and the iodine absorption is high, the beef-form ” of crystals may be taken to afford evidence of the presence of beef or mutton fats. I n the absence of vegetable oil and with a low iodine absorption, the Belfield test can at most afford some reason for suspicion, but no trustworthy evidence of adulteration.