ALBUMENS AND OTHER ORGANIC SUBSTANCES. CREIGHTON. 69 



(d) Experiments ivith gelatine. 



On account of the close relationship between the albumens 

 and the albuminoids, the following experiments were carried 

 out to determine the influence of the presence of the latter 

 substances on reactions of certain iron salts. As a typical 

 albuminoid gelatine was employed. A 10^ solution was found 

 to be quite fluid at 20°. 



'No precipitation of ferric hydroxide occurred on the addi- 

 tion of ammonia to a mixture consisting of equal volumes of 

 1.0^ ferric chloride, Qfc gelatine solution, and distilled water; 

 haematoxylin, however, gave a violet black colouration. In a 

 control experiment ferric hydroxide was precipitated by 

 ammonia. 



1 c. c. of 0.1^ potassium ferricyanide and 5 c. c. of 6^ 

 gelatine solution wore added to 5 c. c. of distilled water. 

 Although the mixture turned blue on the addition of ammonium 

 ferrous sulphate, no precipitate formed. The blue colour dis- 

 appeared from this solution on boiling. With 8 c. c. of 10^ 

 gelatine solution no blue colouration appeared on the addition 

 of ammonium ferrous sulphate to the mixture ; if however, 

 besides the ammonium ferrous sulphate, a few drops of hydro- 

 chloric acid were added, the solution turned blue -and a precipi- 

 tate of Tumbull's blue slowly formed. In the control experi- 

 ments, in which the gelatine solution was replaced by an equal 

 volume of distilled water, a deep blue precipitate was obtained 

 on the addition of the ammonium ferrous sulphate. 



It was found that a mixture containing 5 c. c. of 0.05^ 

 soluble Prussian blue and 5 c. c. Qfc gelatine could be kept at 

 95°-100° for one and a half hours without the blue colour of 

 the solution appreciably decreasing in intensity. With 7 c. c. of 

 10^ gelatine, however, the colour of the Prussian blue faded 

 completely under these conditions. The blue colour of the 

 mixture returned on the addition of a few drops of either dilute 

 hydrochloric acid or hydrogen peroxide. With hydrochloric 



