“In the one process we proceed as follows——We take about one part by weight of anthraquinone and about three parts by weight of sulphuric acid of about specific gravity of 1·488, and introduce the same into a retort, which may be made of glass, or porcelain, or of any other material not easily acted upon by sulphuric acid, and the contents are then to be heated up to about 260° Centigrade, and the temperature is maintained until the mixture is found no longer to contain any appreciable quantity of unaltered anthraquinone. The completion of this operation may be ascertained or tested by withdrawing a small portion of the product from time to time, and continuing the operation at the high temperature until such product upon being diluted with water is found to form a substantially perfect solution, thereby indicating that the anthraquinone has become either entirely or in greater part converted into the desired product. The products thus obtained are then allowed to cool, and are diluted with water; carbonate of lime is then added in order to neutralise and remove the excess of sulphuric acid contained in the solution; the mixture is then filtered, and to the filtrate carbonate of potash, or carbonate of soda, by preference in solution, is to be added until carbonate of lime is no longer precipitated; the mixture is then filtered, and the clear solution is evaporated to dryness, by which means the potash or soda salts of the sulpho-acids of anthraquinone are obtained, and which are to be treated in the following manner:——We take about one part by weight of this product, and from two to three parts by weight of solid caustic, soda, or potash; water may be added or not, but by preference we add as much water as is necessary to dissolve the alkali after admixture; we heat the whole in a suitable vessel, and the heating operation is continued at a temperature of from about 180° to 260° Centigrade, for about one hour, or until a portion of the mixture is found upon withdrawing and testing it to give a solution in water, which being acidulated with an acid, for example, sulphuric acid, will give a copious precipitate of the colouring matters. The heating operation having been found to have been continued for a sufficient time, the resulting products are then dissolved in water, and we either filter or decant the solution of the same, from which we precipitate the colouring matters or artificial alizarin, by means of a mineral or organic acid, such, for example, as sulphuric or acetic acid. The precipitated colouring matters thus obtained are collected in a filter or otherwise, and after having been washed may be employed for the purpose of dyeing and printing, either in the same way as preparations of madder are now used or otherwise.