To dye caoutchouc, or gutta-percha, or their compounds, black, I boil the same from a quarter of an hour to half an hour in the following preparation: I take one pound of sulphate of copper dissolved in one gallon of water, one pound of caustic ammonia, or muriate of ammonia; or I take and boil one pound of sulphate or bisulphate of potash, and half a pound of sulphate of copper with one gallon of water. To dye caoutchouc, or gutta-percha, or their compounds, green, I take one pound of muriate of ammonia, half a pound of sulphate of copper, two pounds of caustic lime, and one gallon of water, and boil as before, from quarter to half an hour. Another dye producing a purple tinge, I obtain by using one pound of sulphate or bisulphate of potash, a quarter of a pound of sulphate of copper, and a quarter of a pound of sulphate of indigo, and boil the caoutchouc, or gutta-percha, or compounds, from one quarter to half an hour. The depth of color may be varied by varying the proportion of the ingredients used. When it is wished to color caoutchouc, or gutta-percha, or their compounds, I employ the following colors, but do not confine myself thereto, nor do I make any claim to the same. For _blue_, those known in commerce as Victoria blue and ultramarine. For _red_, vermillion, carmine or rose lake. For _green_, Brunswick green or acetate of copper. For _yellow_, chrome yellow or oxide uranium. For _white_, the color known as satin white; and I prefer generally to use this color as a _ground_ for the colors above named, and I would here observe, that the coloring processes precede those for “the change.” HANCOCK’S PATENT. To CHARLES HANCOCK of Grosvenor Place, Middlesex, London, for certain improvements in the preparation of gutta-percha, and in the application thereof, alone and in combination with other materials, to manufacturing purposes; which improvements are also applicable to other substances. Sealed, February 10th, 1847. This invention relates, _firstly_, to the methods and machinery employed for preparing gutta-percha for manufacturing purposes. _Secondly_, to certain improvements or processes previously secured to the present patentee, and consisting in sulphuretting gutta-percha, (since called metallo-thionizing) and in applying these improvements to the sulphuretting of caoutchouc and jintawan.