As early as the year 1892 Schlumberger and Sinibaldi proposed the use of Chardonnet silk for the manufacture of mantles; but their patent, a Belgian one,[533] attracted little attention, although they stated clearly that the denitrated silk will readily take up the lighting fluid. Ignorance of this fact deferred the successful application of this fibre for ten years. In 1894 De Mare suggested the preparation of mantles by addition of the necessary salts to the collodion solution before squirting; in the following year Knöfler used the same process, recommending in addition the use of ammonium sulphide to denitrate the impregnated threads. These two attempts, which were found to be unworkable, owing to the difficulty of obtaining a homogeneous product before squirting, were merely efforts to compete against the Auer monopoly, resting on Welsbach’s patents, which covered impregnation of any natural fibre. In Knöfler’s process,[534] the salts were dissolved in alcohol and added to the collodion solution, which was then forced through jets into water, to which ammonia was added to prevent removal of the nitrates in solution; the threads were then denitrated with ammonium sulphide. The ammonia treatment of course converts the nitrates into the insoluble hydroxides, a departure which was followed in most of the numerous patents inspired by Knöfler’s process. [533] _Vide_ Böhm, _Zeitsch. angew. Chem._ 1912, ~25~, 657. Apparently this patent was not taken up; no account of it has been found in the published patents of the Belgian Government. [534] _E._ 11038, 1895, granted July, 1895. The first indications of the method which ultimately led to success are to be found in a patent taken out by Plaisetty, in 1901.[535] The specification protects the addition of thorium and cerium hydroxides to the cuprammonium solution of cellulose, but apparently without any inkling of the results that were to follow, and more or less incidentally, he includes in this patent the impregnation of the finished fabric and the subsequent treatment with ammonia. In the following year he applied for a German patent,[536] which was granted in May, 1903, in which he definitely protects the impregnation of the finished fabric, and the ammonia treatment, the fabric being then washed and dried, and burnt off as usual. [535] _E._ 20747, 1901. [536] _D. R. P._ 141244.