122 ARNAUD AND HAWLEY: NOTES ON THE DETERMINA.TION OF B 42 8 0.5 2 1.0 &4 G NOTES ON THE DETERMINATION OF BUTTER FAT AND COCOANUT OIL IN MARGARINE. -- I BY 3’. W. F. ARNAUD, F.I.C., AND H. HAWLEY, RI.Sc. (Read at the Meeting, February 7 , 1912.) THE method suggested by Cribb and Richards (ANALYST, 1911,36,327) for calculating from the Reichert and Polenske figures the percentage of cocoanut oil and butter fat in margarine mixtures yields excellent results with comparatively large proportions of cocoanut oil, but with quantities under 20 per cent. (the Polenske being below 2.5) the correction applied to the Reichert and Polenske figures is too great. With the aid of the following formulae and of the subjoined curve, deduced from the analysis of a variety of mixtures, the corrected Polenske figure may be obtained and the percentage of cocoanut oil calculated : R 10 P=(P--P”)- - +T.P = corrected Polenske figure. P’ =found Polenske figure. P=Polenske figure of margarine fat free from cocoanut oil and butter T = correction ascertained from curve. (about 0-4). loop Percentage of cocoanut oil = - 17.6 2.0 1.5 1.0 0.6 The butter fat is then found by the following method : R = ( R - R ) - Beichert due to cocoanut oil - T. R = corrected Reichert-Meissl figure. R = found Reichert-Meissl figure. R = Reichert-Meissl figure of margarine free from butter and cocoanut oil T = correction ascertained from curve. (about 0.6). 100R Percentage of butter fat = ~ 25BUTTER FAT AND COCOANUT OIL IN MARGARINE 123 The percentage of butter fat in any margarine mixture may be coufirmed by the Kirschner process, for which purpose the following formula is recommended : K = (IT-0.5) --p in which 10' K = corrected Kirschner figure.K = found Kirschner figure. 0.5 = Kirschner figure of butter-free margarine. P = found Polenske. 100 K Percentage of butter fat = I__ 23 ' DISCUSSION. Mr. c. EL CRIBB said that Mr. Richards and he had referred in their paper to the question of an allowance for the Reichert and Polenske figures of margarine fat in mixtures, but in the mixtures then dealt with there was never less than 20 per cent. of cocoanut oil and 20 per cent. of butter, so that the correction would be very small, and it seemed scarcely worth while to make it ; but when the proportion of margarine might be as high as 90 per cent. it became necessary to take the correction into account. Mr. E. R. BOLTON said that due regard must be had to the composition of the margarine. Margarine nowadays often contained notable quantities of lard, and, although lard itself had a very low Reichert-Meissl value, it exercised, when mixed with other fats, a curious altering effect on the volatile fatty acids.