188 THE ANALYST. ON THE RELATION BETWEEN DR. KOETTSTORFER’S PROCESS OF BUTTER ASSAY, AND THE OLD PROCESSES. BY G. W. WIGNER, F.C.S. Rend before the Society of Public Analysts, at 8 l ~ J i i e l d , on 22nd Ampist, 1879. DR. KOETTSTORFER’S process appeared to me likely to prove very valuable in the ordinary analyses of butter, by at least disposing without further labour of most of the genuine samples; but it was obviously impossible to adopt a new process as a basis of an adverse report, uutil it had been thorouglily tested.I t appeared to me, that the most practical mode of testing it mas to submit to this process (in addition to the tests which would otlierwisz have been made) every sample of butter or other fat which was received. I thcre€ore adopted it as an auxiliary process, and have examined nearly 100 samples by it.As a general opinion, I may state that I am well pleased with the process for the piwpose above mentioned. It is not, however, free from its veak points, Carbonic acid acts very much on the colour of phenol-phthalein, and, in order to cnsure fair accuracy, it is essential that the fat slionld be saponified with the alcoholic potash solution in a flask, wliicli certainly ought to be corked with a cork having a notch in the sidc.While tlie alcohol itself is boiling pretty freely there is, of course, no risk of carbonation, but, as soon as the water is adcied to clilnte the soap for titration, tlie risk increases greatly. My experience also indicates the necessity for the use of n very large excess of potash solution, an excess very much larger than mould be ordinarily employed when the fatty acids were to be weighed.It appears desirable to use at least twice as much potash as would be actually required to combine with tlie soap present. Again, in reference to the potash solution itself. I find that a very small amount of colour seriously masks the end of the titration, and it becomes essential to use pure potash, and to keep the solution in hard glass bottles, so as to prevent the additional colour which is often imparted by the decomposition of the glass of comruoii Winchesters, Taking all tliese precautions, however, I find the process a useful one.But I must call special attention to tlie following exceptions :-It is comparatively useless when applied to old samples of butter, which have been alternately heated, and cooled; and, even in the cases of lard and butterine, repeated heating exercises a inom uncertain effect than it does 011 tlie fatty ncid determinntioiz ; but, although useful, it can never come iiito general use as a substitute for the determinations of fattr acids and solablc acids, because any alkalies added to the fat, mhether frandnlentl~, or for supposeJ preservative purposes, entirely upset tlie estimation.Therefore, while it inay bc-and in my opinion is, when properly carried out--a safe process 011 which to pass a buticr RS genuine, it is quite unreliable as a proof that the butter is adulterated. The admixture of three per cent. of carbonate of soda with the salt added to the butter, will, by this process, change the results so much, that a genuine buttel.moul~ be coiidemneil ; 2nd such a perceutage of admixture is one that has been used, while smaller percentages are corninon,THE ANALYST. 183 By the fatty acids’ process, sncli an acliuiskure would liave scarcely any sensible effect, but it ~vould exercise a very important effect on the actual density of the fat, and, indeed, in certain cases, might render the determination of actual density quite fallacious.Unfortunately merely testing the water present in the sample of butter for alkalinity is not sufficient to prove Ivvhetlier alkaline carbonates have been added, and no test seems readily available. I have, therefore, come to the conclusion that it is unsafe and unjust to condemn any sample of butter as adulterated on either the titration or specific gravity processes.I€ the sample passes these tests well it may be relied on as genuine, but it may fail to answer both tests, and yet have no foreign fat mixed with it. In such a case, a full determhiation of loth soluble and insoluble fatty acids, is the only safe course to adopt. Of course, therefore, I view the relation between the actual density, fatty acids and titration results as a matter of no great importance in adulterated samples, but in genuine samples it is otlierwise.Dr, Koettstorfer found tlizlt tlie amount of KHO required by genuine butters ranged from 23.24 to 22-15 per cent. I t is, of course, with the lowest limits only that we have to concern ourselves, and iny oyhion is, that tliis limit is not low enough eveu in the case of fresh saiuples, and that it is very seriously deficient in the case of samples wliicli liavc been kept and s-abjected to even moderate variations of temperature.I have had seveml samples of butter apparently recently made, a d , certainly, h good condition, wliicli have required 2,s little as 21.34, 21.36, 21.50 per cent.of KHO to saponify them, and which have yet given less than 89 per cent. of fatty acids by the flask washing process, and which, independently of the otlier conditions, I certainly would not condemn as adulterated. In my opinion, therefore, the titration process can only be relied on mlien it shows figures liigher than Koettstorfer has put as the limits. As, however, three samples out of every four received are probably genuine, tlio process may be advantageously used for passing these pure samples, provided proper care is taken to carry tlio analysis further if these results are adverse, and it is for this purpose only that tlie process can come into general use. I think that any sample of butter fat, which requires more than 22.60 per cent. KHO for saponification, as determined by the titration process, may safely be passed as genuine ; but that any lower result should be checked by tt full analysis.