Remarks (1) Exact point of liquefaction difficult to observe; therefore the average of several readings must be taken. (2) Work from the Imperial Office of Health 1907, 26, 444-463. (3) Work out of the Imperial Office of Health 1904, 20, 545-558. (4) Central Journal for Germany 1908, 36, 100. (5) Journal for Popular Chemistry 1907, 16, 308. (6) Obtained at the expiration of a four weeks’ treatment as recommended by Erlenmeyer. (7) Non-volatile fatty acids, insoluble in water, from the determination of the Reichert-Meissl number. (8) Obtained as under a). Freezing Point in various cases, 1 to 8 equals 47·8—Melting Point minus Freezing Point: 52·3-47·8 4·5. We have already stated that there is also cacao fat in the shells, and though it only amounts to some four or five percent, it has long been the care of experimenters to recover and realise that little as fully as possible. It is commercially known as Dutch IIa or artificial cacao butter, and cannot be obtained like the fat of the kernel by mechanical means, but is obtained by some cheap solvent like benzene. The traces of benzene are very difficult to hide, and consequently this shell butter has little commercial value and its manufacture is unremunerative. Filsinger[45] gives the iodine value of shell butter as higher than that of kernel butter, and fixes it between 39 and 40: its acid value, especially if the fat is rancid, can reach 50-60° Burstyn, i. e. 50 to 60 ccm. normal alkali for 100 grammes of fat.[46] If the free acid of shell butter be counteracted with sodium or magnesium carbonate, the neutral fat then has the normal iodine value of pure cacao butter, namely 36·5. In a sample giving an abnormally high iodine value it is always necessary to determine the acid value, and if the latter be too high, the fatty acids must be removed, when if the sample be unadulterated, the normal iodine value will be obtained. It may be noted in passing that the high acid values occurring in shell butter may be due in part to the acidity of the benzene employed as a solvent. Cacao butter has a considerable commercial value, and is consequently liable to adulteration with many inferior fats of vegetable origin. Among these are especially beef and mutton tallow, the purified fatty acids of palm-nut oil, wax, paraffin, stearic acid, dicka fat (nucoa butter, possibly) and cocoa-nut fat, as well as the numerous preparations of the last named, variously known in commerce as Mannheim cocoa-nut butter, vegetaline, lactine, finest plant butter, chocolate butter, laureol vegetable butter, palmin, kunerol etc. Other but less commoner are the sesame cotton-seed, arachidic, margarine and hazelnut oils.