tf PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



the presence of glyoxylic acid in the glacial acetic acid. If 

 the reaction does not take place, add a small amount of a 

 solution of oxalic acid which has been previously treated with 

 sodium amalgam. 



5. Liebermann's Reaction. Add to the other half of the 

 albumin, treated with alcohol and ether, a few cubic centi- 

 meters of fuming hydrochloric acid and warm: bluish to blue 

 solution, which, on standing, becomes paler or more violet 

 or brownish. Sometimes only the violet color appears. 



6. Detection of Nitrogen. A small portion of the albumin, 

 which has been previously treated with alcohol and ether and 

 then dried, is mixed with five to ten times its volume of soda- 

 lime and the mixture heated in a narrow dry test-tube. Am- 

 monia is given off (odor; alkaline reaction of the gas; fumes 

 which it forms when brought into contact with a glass rod 

 moistened with hydrochloric acid; blackening of a piece of 

 filter-paper moistened with a solution of mercurous nitrate.) 



The test for nitrogen with soda-lime fails in the case of 

 certain forms of combination of nitrogen, e.g., with the nitro 

 compounds. Of more general application and also more 

 delicate is the Lassaigne Test. Heat the substance with a 

 small piece of potassium (or sodium) in a narrow test-tube. 

 A violent reaction takes place. After the test-tube has 

 cooled somewhat, dip it into 10 cc. of water contained in a 

 .small beaker; the test-tube breaks and its contents dissolve 

 in the water. When nitrogen is present the solution will con- 

 tain potassium cyanide. Filter the solution, add a drop of 

 ferric chloride solution and a few drops of ferrous sulphate 

 solution to the filtrate and warm. The potassium cyanide 

 forms potassium ferrocyanide. Cool the solution and acidify 

 with hydrochloric acid. Green or blue color or a blue pre- 

 cipitate due to the formation of Prussian blue. 



7. Detection of Sulphur. 1. Heat a very small piece of 

 .albumin in a narrow hard-glass test-tube, the upper part of 



