4®4 Dr. Bolley on the Theory of Dyeing) 



sian blue) ; only with the difference that the section, as com- 

 pared with the external surface, was even less deeply tinged. 



No discoloration of the substance of the cell-walls could, how- 

 ever, be observed in the case of indigo-blue, Turkey-red, madder, 

 pink and violet, chrome-yellow, chrome-black, catechu-brown, 

 nankeen (hydi*ated peroxide of iron), iron-black, and other dyes. 

 With these dyes, colouring in the hollow of the Hbrc was ob- 

 served very seldom, and, we may say, only locally. This appear- 

 ance, on the contrary, presented itself unmistakeably in the case 

 of those specimens of cotton which had been dyed with murexide. 

 The cell-walls themselves were not coloured ; the dye and mor- 

 dant adhered for the most part to the outside surface, but a con- 

 siderable quantity had penetrated into the hollow of the fibre. 

 Fig. 5 will give an idea of the appearance of this section. Of 

 course, therefore, W. Crum's view is not to be approved. Of the 

 two parallel canals lying along the sides of the flattened fibre 

 there is not a trace. 



The method of conducting the investigation by means of sec- 

 tions leaves room for some uncertainty, since in certain cases, where 

 the section is not quite perpendicular, the inclined portion of the 

 outside surface shines through the sharpened edge of the section. 

 The following plan may, in my opinion, be regarded as safer. 

 Solution of oxide of copper in ammonia, according to the obser- 

 vation of E. Schweitzer, dissolves cotton, the cellulose precipitated 

 from the solution being disorganized and gelatinous. Under the 

 microscope this reagent seems to act just like iodine and sul- 

 phuric acid. The appearances which accompany this reaction, 

 v^hich Dr. Cramer* describes very accurately, are altogether 

 similar to those which arc presented when sulphuric acid of 

 proper strength is suffered to act in the presence of iodine. The 

 cuprate of ammoniaf, however, has the advantage of acting 

 much less powerfully in decomposing or dissolving most of the 

 pigments used in dyeing and the metallic oxides of the mordants. 

 Some of them, however (safflower, for example), are unable to 

 resist its action. 



I must here in the first place expressly declare that I cannot 

 understand the statement of Schlossberger J when he says, "So 

 cotton, which I had steeped in a solution of NaCl; NH'* 0, NO^ 



* " On the behaviour of Cuprate of Ammonia towards the Cell-mem- 

 branes of Plants," by Dr. C. Cramer, Vierteljahrschrift der Naturforsch. 

 Gesellschaft in Zurich, 1857; nnAErdmann, Journal fur Prakt. Chemie, 

 vol. Ixxiii. p. 1. 



t I have long made use of a small glass containing a quantity of cuprous 

 oxide, and three-fourths full of a strong solution of ammonia. On shaking 

 the mixture repeatedly and reopening the glass, we have a very convenient 

 reagent, which retains its strength for a long time. 



X Joiirnalfur Prakt, Chemie, vol. Ixxiii. p. 372. 



