(7) A method due to Köchlin is described in the following terms:--An aqueous solution of sulphate of copper is made by adding 100 grammes of the salt to 500 cc. of water. To this, when solution is complete, is added 187½ cc. of a solution of arsenite of soda, which is of the strength represented by 500 grammes of arsenite in 1 litre of water. The result is that a precipitate of arsenite of copper is thrown down. This precipitate is treated with 62 cc. of acetic acid at 11° to 12° Tw., or half that quantity of pure formic acid, for one hour, at a temperature ranging from 104° to 122° F. The pigment thus produced is of good colour, but its superiority would not seem to justify the use of such an expensive article as pure formic acid, nor the minute adjustment of the proportions of the ingredients, in an operation to be conducted on a commercial scale. (8) Another complicated process has been invented by Prof. Galloway, which, under skilled supervision, and when the correct proportions of the several ingredients have been ascertained by careful experiment, may give good results, but several precautions have to be observed which cannot be entrusted to ordinary factory hands. The principle of the process is that when a quantity of sulphate of copper is dissolved in water, sufficient carbonate of soda is added to throw down one-fourth of that copper sulphate as carbonate of copper, and then so much acetic acid is introduced as will convert that copper carbonate into acetate. In order to convert the balance of the copper sulphate into arsenite, a solution of arsenic in boiling carbonate of soda is made and added to the copper acetate solution, both solutions being at a boiling temperature. Emerald green is a pigment which possesses considerable stability in dry pure air, but in damp atmospheres it becomes brown; in the presence of acid or ammoniacal vapours it turns blue, and under the influence of sulphuretted hydrogen it blackens; moreover, strong alkalies destroy it. Consequently it cannot be used in many situations, nor in association with such pigments as contain sulphur compounds. In decorative painting it is difficult to apply on large flat surfaces, and necessitates stippling in order to get it to lie well; but when stippled on a ground of proper green it develops an exceedingly beautiful bloom-like appearance. Its peculiar shade distinguishes it from all other green pigments, none of which approaches it in the paleness and brightness of its colour. It can be distinguished by the fact that it is soluble in acids and ammonia, to a blue solution which does not change on boiling. In caustic soda it also dissolves with a blue colour: on boiling, a red precipitate of cuprous oxide falls down. No other green pigment answers to all these tests.