428 ALBUMINOUS COMPOUNDS. 



acetic acid is to be added befor^boiling, excess being carefully 

 avoided. 



2. If complete coagulation is not produced by boiling with 

 acetic acid alone, an equal volume of concentrated solution of 

 sodium sulphate may be added, and the liquid again boiled. 



** 12. Tests for traces of Albumin in solution. 1. 

 !, nnd (Jwtfier Test. It is advisable, before try- 

 ing this test, which is also used for the detection of sugar, to 

 become acquainted with the reaction presented when a caustic 

 alkali is added to a solution of cupric sulphate, and the mix- 

 ture heated without any foreign substance being present in 

 the solution. Put a little distilled water into a test-tube, with 

 a drop or two of a dilute solution of cupric sulphate. Pour 

 me liquor potassie. and a light blue precipitate of 

 hydrated cuprie oxide will be thrown down. Boil the liquid, 

 and the blue precipitate will be converted into a black powder, 

 which is anhydrous cupric oxide. If it is gently warmed, in- 

 stead of 1 toiled, the powder will be dark brown. 



Tin- hydrated cupric oxide is not soluble in excess of ordi- 

 nary liy>iu .!, hut, is slightly soluble in very concen- 

 trated solutions of potash, and imparts to them a light blue 

 color. The. presence of eertain organic substances renders 

 hydrated cupric Milphate soluble in weaker alkaline solutions. 

 Put >oim' water and cupric sulphate solution in a test-tube; 

 add a small crystal of tartaric acid, or a few drops of its solu- 

 tion, and then liquor_j)otassa'. Kither no precipitate will form, 

 or it will i . and. on shaking the tube, the liquid will 

 become of a bright blue color. Boil it: no precipitate will fall, 

 and no change in the color will take place. 



Ali/'li'-alian of Hi in Text /<> Allnmu' n. Put some solution of 

 albumin in a test-tube; add a drop or two of cupric sulphate 

 and liquor potassa- ; an excess of liquor potassie does not inter- 

 fere with the reaction. Kither no precipitate will fall, or it 

 will be dissolved on shaking the tube, the liquid assuming a 

 violet color. Boil it. No precipitate falls, but the violet 

 color will become deeper. 



** 2. Xntil1iin'nii-in Ilt'arlinn. Add to the fluid some con- 

 centrated nitric acid, and boil. Let the liquid cool, and then 

 add a little ammonia. If albumin is present, an orajjg_mlor 

 will be produced. This is one of the most delicate tests for 

 albuminous substances. 



** :{. MiWm'x IlrnrtioH. Add to the fluid a little of Mil- 

 Ion's reagent and heat. If albumin be present in considerable 

 quantities, a white precipitate will fall and become red on heat- 

 ing ; if only a trace be present, the iluid will become red. The 

 lor i-i produced even at ordinary temperatures, but it is. 

 increased by heating. 



To prepare Millon's reagent take two beakers, one of which 



