Samuel Blatchford

“ In the second process anthracine is heated with sulphuric acid, the product is put in solution, and treated with peroxide of manganese, under heat. Caustic lime is then added in excess, till there is an alkaline reaction, the mixture is then filtered and carbonate of potash or soda is added to it, and the potash or soda salts of the sulpho-acids of anthrakinon are produced. These are treated with caustic potash or soda, under heat, the product is put is solution, and the artificial alizarine is precipitated by an acid. ”

“ Perkin noticed the same fact shortly after or at about the same time. This method was further developed by Caro and the original discoverers, and the English patent was taken on June 25, 1869, (Caro, Graebe and Liebermann, English patent, 1869, No. 1,936.) The patent of Perkin is dated June 26 (Perkin, English patent, 1869, No. 1,948.) Two methods were discovered, analogous to the two bromine methods. In the first and most important, the anthracine is oxydized to anthrachinon; this is converted into sulpho-acids by heating with sulphuric acid to 200 deg. to 260 deg. ”

“ There is no suggestion of anthrapurpurine or isopurpurine, or of any process for producing them. Their published statements show that it was the synthesis of the alizarine of madder which they were making, the specification of No. 95,465 shows that and nothing else,-and it is not contended that the alizarine of madder contains anthrapurpurine or isopurpurine. ”

“ The first process is, therefore, identical with the first bromine method given above. In the second method the sulphuric acid acts on the anthrachinon in such a manner that, besides the anthrachinon monosulpho-acid, as principal product, a small amount of anthrachinon bisulpho-acid is also formed. This was subsequently determined analytically by Graebe and Liebermann. In the patent only the anthrachinon sulpho-acids are mentioned. From analogy, Perkin, in his paper, (Jour. Chem. Soc. (2) viii, 133, and Ann. Chem. Pharm. clviii. 335.) considered the bisulpho-acid only. ”

“ The English patent to Caro and Graebe and Liebermann having been granted June 25, 1869, and the full specification filed January 13, 1870, an application for a patent in the United States for producing artificial alizarine by the sulpho-acid processes was filed by them January 26, 1870. ”