Whilst it is very generally agreed that the addition of titanium results in the production of much stronger and more durable products, the question of the precise effect obtained is by no means definitely settled. The experimental work, whilst pointing on the whole to the superiority of titanium-treated steel, is by no means conclusive; in some cases, indeed, it is conflicting. Thus the micro-photographs obtained by von Maltitz[620] and Venator[621] show that the titanium-treated steel has a far cleaner fracture and far more homogeneous structure than steels not so treated; on the other hand, the micro-photographs of Treuheit[622] show practically no improvement in structure for the titanium steel. The exhaustive tests of the first two authors, again, and the experiments of numerous railways in the use of titanium steel rails,[623] demonstrate clearly that the treatment results in improvement in strength and durability of the product; but the work of Otto[624] proves equally clearly that his products did not differ markedly, whether titanium-treated or not, and he is of opinion that the rail tests were not sufficiently prolonged or searching to be considered conclusive. It is nevertheless to be considered certain that the use of titanium does cause a marked improvement in the quality of the steels obtained, and especially in the durability of rails. The negative results obtained by some authors may be explained, firstly, on the ground that no tests are conclusive unless carried out with steel from the one bath, one half of which has been treated with titanium, and the other half not so treated; secondly, that the ferro-titanium must be incorporated with the metal, and must not be suffered to be taken up by the slag, and so lost; and thirdly, that the bath must be allowed to remain for some minutes after treatment, in order that the reaction may be complete, and the titanium-bearing slag allowed to rise to the surface. When these conditions are carefully observed, experiment shows that marked improvement in the quality of the steels produced is effected. [620] _Stahl Eisen_, 1910, ~29~, 1593. [621] _Ibid._ 1910, ~30~, 650. [622] _Ibid._ 1910, ~30~, 1192. [623] _Vide_ Dudley, _J. Ind. Eng. Chem._ 1910, ~2~, 299; also _Cass. Mag._ 1911, ~40~, 483. [624] _Vide_ abstract in _Stahl Eisen_, 1912, ~32~, 1497.