Compared to the analysis of crude Neradol containing sulphuric acid, the figures show that, on the one hand, the presence of the comparatively small quantity of sodium acetate but slightly influences the contents of non-tannins and water, but, on the other hand, reduces the contents of tannins and also the acidity. The tanning intensity of this product, however, is considerably increased, and using a 1° Bé. solution a leather is obtained in a very short time very similar to that yielded by ordinary Neradol D, but considerably harder; the latter property is due to higher acidity and almost complete absence of salts in the product treated with sodium acetate. The author finally attempted to partly neutralise crude Neradol with various hydroxides and carried out tanning tests with samples containing the different metals. Hardly any difference in the finished leathers could be observed as regards colour or quality; the tannage could by no means be described as that of a combination of Neradol D and the respective metals. 12. Neutral Neradol Crude Neradol, completely neutralised with caustic soda, yields a product of the following composition:-- Tanning matters 19.8 per cent. Soluble non-tannins 37.9 " Insolubles 0.0 " Water 42.3 " ------------ 100.0 per cent. The qualitative reactions of this product differ from those of non-neutralised Neradol to the extent that gelatine is not precipitated and iron salts are not coloured blue, but dirty brown, by the aqueous solution of this product. The completely neutralised product, diluted to various concentrations (of 1°, 2°, 3°, and 5° Bé.) and tested as to tanning properties, revealed the surprising fact that the pelts were not even surface tanned, and were coloured evenly blue throughout by indigotine. It might have been anticipated that sodium dicresylmethanedisulphonate would be as devoid of tanning powers as is a neutralised vegetable tannin, but it is difficult to explain the fact of the sodium salt being adsorbed by hide powder as "tanning matters" in the Official Method of Analysis. Brought to a logical conclusion, the figure 19.8 per cent, should be deducted from 32.5 per cent, obtained in the analysis of a _partly_ neutralised Neradol D, which comparatively large quantities of the sodium sulphonate also adsorbed by hide powder, leaving the "tanning matters" of Neradol D at 13.5 per cent. This diminished figure, however, does in no way reduce the value as a tanning agent of Neradol D; it merely shows how inadequate is the hide powder method of analysis when applied to substances of the composition of Neradol D. This is further confirmed by the Loewenthal permanganate method, which yields the following figures:-- Tanning matters 7.2 per cent. Soluble non-tannins 59.1 [Footnote: Collegium, 1913, 521,487.]