the dark. It may be that in the dark the leuco I I compound is not completely oxidised.

As regards (2), the possibility of oxy com- pounds being produced is proved by the behaviour of dimethylaniline, which, heated with hydrogen peroxide to 60’-70” C., yields dimethylaniline oxide C,H, N(CH,),, the com-

II

~ _ _

the equilibrium may he SO disturbed an to favour -:ie red aeries, and tlie deepening of the shark

0 position of which is clear, as i t is readily reduced to dimethylaniline again.

Similar tertiary amines give similar oxy com- pounds. The initial deepening of the shade is, however, specifically an action of light, for I have been able to prove that a dyestuff solution, treated with hyrdogen peroxide and kept in the dark, became lighter, but that the shade deep- ened upon exposure to light. Placed again in the dark, it became lighter, but exposure to light again restored the colour.

With regard to (3), we may have, with dye- stuffs of the nitrophenol class, changes into pseudo compounds : these are tautomeric hydro- gen compounds, as they yield two series of structurally isomeric esters. Hantesch hae shown that the ester of nitrophenol is colourless, whilst the aci-nitrophenol ester is intensely red coloured. From this he concludes that the corresponding hydrogen compounds would show the same difference.

Nitrophenol Aoi-Nitrophenol .OH 1.0

C H Y ‘\NO.OH ~ -~~

Colourless. Coloured (quinonoid).

The deepening of shade occurring by sall formation in the case of nitrophenols he explah as follows :-Where in the case of salt formatior from a compound containing hydroxyl there ir a deepening of the colour (or colour is firs( apparent), this indicates that by the salt forma tion there has been brought about a change ir the original substance, leading to a more stronglj acid, chromophoric atomic grouping.

This h,ypothesia is supported by Baly (“Ab sorption Effects in the Ultraviolet,” Chem. Soc. 89,618-621). Hantzsch thinksfrom hislater worl (Ber. 40, 330-361) that in the aci-compound we have to deal with stereo-isomers, and tha with all probability we can assume the existencc of the following configurations :-

colourless. Red. Yellow.

In no case is one form more symmetrical thai another, and therefore to be considered as mor favourable to existence. One series may easq be converted into another. In the nitrophenol the ortho position seems to favour the existenc of the red form, and under the influenae of ligh

., e thus explained. The statements in the literature with reference

3 the deepening of the shade of nitrophenol ompounds deal chiefly with the behaviour of ’icric Acid, with additions of oxalic or tartaric cid, or Picric Acid gelatine, but I have been able D obtain a deepening with pure Picric Acid ontained in carefully cleaned Conductivity .essels. The change was accompanied by n iqinution in the conductivity up to a certain Ioint, when it remained constant. Pure trinitro- bhenol is a stronger acid than aci-trinitrophenol.

With respect to the additions of acids which #re themselves susceptible to light (oxalic), the iddition may bring about a change in the dis- ociation conditions, accompanied by a lowering If the colour intensity, but in consequence of he effects exerted by the decomposition pro- Lucts of the oxalic acid, the shade of the picric loid solution may appear to be deeper. With m addition of acetic acid the expected diminu- ,ion in the intensity of the shade occurred.

Sometimes the deepening of the shade iH ,raceable to the oxidation of impurities, as I have ieen able to show is tlie case with Uranin.

Elbetracts front Englteb atrb $orefgn 30~1~11+3 aitb patents.

I.-MACHINERY AND APPARATUS.

Improvements in Machines for Dyeing, Bleach- ing, Washing, or similarly Treating Textlle Fabrics or other Materials or Substances.

J. W. BALME and C. H. ASHTON.

This describes a jigger made of glazed earthen- ware or fireclay, preferably made in one piece. The figure shows a transverse section of the maahine. Instead of using a steam-pipe a hollow passage 1 is moulded in, having an inlet

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passage 2 leading to the exterior for attach- ment of a steam supply, and perforations 3 at intervals to permit uniform distribution of the steam. The vessel is provided with in-