=Copper Arsenite.=—The compounds of arsenious acid with copper are among the most handsome and bright colours which exist. It is thus to be regretted that these pigments are disappearing more and more, and indeed with every reason, from the pigments permitted by law. In the end they must fall into complete disuse. It is a matter of common report that these pigments, and particularly emerald green, have frequently caused arsenical poisoning. Numbers of people have been repeatedly made ill by the dust of emerald green fixed on light fabrics, such as are used for ball dresses, simply by albumin or dextrine, and brought into the air by the movements of the dancers. It has been further shown that the air of rooms papered with hangings coloured by emerald green contains small quantities of the most poisonous of all arsenic compounds, arseniuretted hydrogen. Although it is in the interest of colour makers to produce the brightest possible colours, yet, on account of their dangerous properties, pigments containing arsenic should be quite excluded. In several countries their use is forbidden by law. Since there are several pigments which can compete in brightness with the arsenic colours, it is to be hoped that the latter will shortly disappear from commerce. =Scheele’s Green, Swedish Green.=—A solution of 32 parts of potash is boiled with 11 parts of white arsenic (arsenious acid) until the latter is completely dissolved. This solution of potassium arsenite is mixed with a hot solution of 32 parts of copper sulphate free from iron. The beautiful green precipitate is washed with hot water and dried. These directions for the preparation of copper arsenite are due to Scheele, the discoverer of the pigment. It can be prepared by several other methods. When white arsenic and copper sulphate are dissolved together, and caustic soda added to the boiling solution, Scheele’s green is precipitated. When made by this method the pigment must be very carefully washed; if the excess of caustic soda is not completely removed it is very hard when dry, and is difficult to powder. In order to obtain darker greens the quantity of copper sulphate is increased. A particularly bright green is obtained by dissolving copper sulphate in water, with the addition of 12 to 15 per cent. of white arsenic, and precipitating by a solution of potassium zincate, which is obtained by boiling caustic potash solution with zinc filings, hydrogen being evolved.