34 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



(a) Reactions with Methyl Violet (0.5 : 1000) or Gentian 



Violet. 



1. A small portion of the hydrochloric acid solution A in 

 a test-tube is treated with a few drops of methyl violet solu- 

 tion: steel-blue color. Make the same test with water: 

 violet color. With the lactic acid solution: violet with a 

 light-bluish tint. 



2. Influence of Dilution. Repeat experiment I with the 

 hydrochloric acid solution B. 



3. Influence of the Presence of Albumoses and Peptone. 

 Dilute some of the hydrochloric acid solution A with an 

 equal volume of water, and another portion with an equal 

 volume of the peptone solution, then add a few drops of the 

 methyl violet solution to both and compare the colors. We 

 may also perform the experiment by taking some of the steel- 

 blue solution, produced by the action of the hydrochloric 

 acid (A) on the methyl violet solution, dividing it into two 

 parts, and adding the peptone solution to one part and water 

 to the other part. 



4. Influence of the Peptone in very dilute Hydrochloric 

 Acid. Repeat experiment 3 with the hydrochloric acid 

 solution B. From the results in 3 and 4 it will be seen that 

 the methyl violet reaction cannot be used in the presence of 

 considerable quantities of albumoses and peptone. 



5. (a) To about 30 cc. of the lactic acid solution add 

 some of the methyl violet solution and divide the mixture 

 into three parts. To the first, A', add an equal volume of 

 water; to the second, B', the same volume of water and then 

 saturate the mixture with salt (NaCl); to the third, C', the 

 same volume of a 3 per cent, salt solution. A' does not 

 change its color, it only becomes somewhat clearer; C con- 

 ducts itself in the same way ; B', however, becomes perceptibly 

 steel-blue. Conclusion: sodium chloride in the presence of 



