If these two acids be separated from each other in a chemical way we obtain glycocholic acid, an acid free of sulphur and the other taurocholic acid containing sulphur. The alkali salts contained in bile are quite soluble in water or alcohol but insoluble in ether. To produce it in a pure state mix the bile with as much animal coal, (spodium) so that finally, on evaporation in the water-bath a dry powder results, from which is drawn, by the use of absolute alcohol, the now colorless cholic acid esters, cholesterine, choline, lactic acid, etc. When ether containing a little water is added, the cholic acid esters are precipitated as colorless plaster-like masses and crystallize, when left in the fluid for some time. The so-called crystallized bile is the final material for the preparation of acids. The acids of ox-gall have been investigated in the most thorough manner. Glycocholic acid is obtained as a colorless precipitate from a watery solution of crystallized ox-gall, by adding dilute sulphuric acid until the fluid becomes flocculent, which after a while, especially, if the water contains a little ether, is changed into a voluminous 'magma' of fine white needles. If collected upon a filter, these needles unite and form a lustrous felt. Glycocholic acid is sparingly soluble in water but soluble in alcohol. It forms the principal constituent of bile, it reacts feebly with acid and tastes bitter-sweet. Taurocholic acid is found only in small quantities in ox-gall and has no important effect on the colors. THE EFFECT OF OX-GALL UPON COLORS. By chemical analysis we have seen that glycocholic acid is the principal constituent of ox-gall and in combination with taurocholic acid, glycin, choline and lactic acid is soluble in water. On the other hand, when pure, it is soluble with difficulty and therefore is only of use to us when in combination with other acids, as it must combine intimately with water-colors. The atomic weight of gall and the insolubility of pure glycocholic acid in water are the most valuable properties of it for the marbling colors. The first gives to the colors the expanding power, the latter the adhesion to paper. All the lower fatty acids, among which ox-gall may be numbered, possess properties similar to fatty bodies, namely a less atomic weight than water. They differ from fatty bodies in this, that they mix with water. The expanding power and lightness of ox-gall are, consequently, peculiarities of equal value. Marbling size forms the base for the colors, which by the consistency of the glutinous mass and by the gall added to them are prevented from sinking to the bottom. They float like drops of oil upon the water and only differ from them by the fact that the colors will spread out on the size, while the drops of oil on the water are contracted to circular spots of small size. If a drop of oil were thrown upon the size it would spread out very quickly.