897 



iDinatioiis could be executed directly — without having to dilute. 



Further it was shown that the quantity of dyestuff taken up 



depends on the concentration of the electi-olyte, hoivever only to <i 



Cone, of 

 benzopurpurine. 



Change of the intensity of colour. 



Taken up by the 

 fibre. 



certain limit; an increase of concentration above 10 niilliniol. in 

 many cases does not cause a rise of the quantity of purpurin which 

 is precipitated on the cotton. 



A close investigation will have to decide whether this is due to 

 a saturation of the cotton fibre with the electrolyte, by which a 

 further rise of the cone, in the bath leaves the concentration in the 

 fibre practically unchanged, in consequence of which the precipi- 

 tating action cannot exceed a certain figure. 



We shall not enter into further detail because this falls outside 

 the scope of this communication. 



A. Comparison of the action of Mi^SO^ 1 aq, {CdSOt),SH^O 



and Zn SO^ 7 aq. 



Here several concentrations of the salts were used and for the 

 rest the exhaustion of the bath (1 mg. purpurin per 500 ccm.) was 

 defined as mentioned above. From this the quantity of dyestuft taken 

 up by the cotton (1 gram; always at 65° during 10 minutes) was 

 calculated by subtraction. 



If, for example, it was found that a column of 15 cm. after dyeing 

 had the same intensity of colour as 9.2 cm. before dyeing, then 

 there was present in the bath 9.2/15 >; 100% = 61. 5Vo and hence 

 the fibre had taken up 38.57,- 



The determinations mentioned above were moreover controlled 

 by comparing several of the exhausted solutions with each other. 



So 15 cm. of the ZnSO, sol. of 0.25 millimol. should be equal 

 to 14.5 cm. of the equimol. MgSO, sol.; 15 cm. of the ZnSO, sol. 

 0.33 millimol. = 13.4 cm. of the equimol. CdSO, sol. and = 13.2 cm. 

 of the equimol. MgSO^ sol. etc., which was always the case. 



