to A MANUAL OF PHYSIOLOGY 



is produced. It can be derived by similar treatment from any 

 albumin or globulin. 



(a) Neutralize, after colouring with litmus solution, by the addition 

 of dilute hydrochloric or acetic acid. Alkali-albumin is precipitated 

 when neutralization has been reached. It is redissolved in excess 

 of the acid. 



(/3) To another portion of the solution of alkali-albumin add a few 

 drops of sodium phosphate solution, then litmus, and then dilute acid 

 till the alkali-albumin is precipitated. More of the dilute acid should 

 now be required to precipitate the alkali-albumin, since the sodium 

 phosphate must first be changed into acid sodium phosphate. 



(7) On heating the solution of alkali-albumin there is no coagula- 

 tion. 



(2) Proteoses. For preparation and reactions, see p. 426. They 

 differ from albumins and globulins in not being coagulated by heat, 

 and from meta-proteins in not being precipitated by neutralization. 

 They are soluble (with the exception of hetero-albumose) in distilled 

 water, and are not precipitated by saturation of their solutions with 

 magnesium sulphate or sodium chloride. Saturation with ammonium 

 sulphate precipitates them. With a solution of commercial ' pep- 

 tone,' which consists chiefly of albumoses, and contains only a little 

 true peptone, perform the following tests : 



(a) Boil the slightly acidulated solution ; there is no coagulation. 



(p) Biuret reaction, p. 7. 



(7) To a portion of the solution add its own volume of saturated 

 ammonium sulphate solution. The primary albumoses (proto- and 

 hetero-albumose) are precipitated. Filter. Add a drop of sulphuric 

 acid to the filtrate and saturate it with ammonium sulphate crystals. 

 The secondary or deutero-albumoses are precipitated. Filter. The 

 filtrate still contains peptones. Use it for (3). 



(3) Peptones. For preparation and tests, see p. 426. They differ 

 from heat-coagulable proteins and meta-proteins in the same way as 

 proteoses, and they differ from proteoses in not being precipitated by 

 ammonium sulphate. On the filtrate from (2) perform the biuret 

 test, as described in (7), p. 8 ; and note that the pink colour is the 

 same as that given by proteoses. 



Carbo-hydrates. 



1. Glucose or Dextrose. Make a solution of dextrose in water, 

 and apply to it Trommer's test for reducing sugar. Put some of 

 the dextrose solution in a test-tube, then a few drops of cupric 

 sulphate, and then excess of sodium or potassium hydroxide. The 

 blue precipitate of cupric hydroxide which is first thrown down is 

 immediately dissolved in the presence of dextrose and many other 

 organic substances. Now boil the blue liquid, and a yellow or red 

 precipitate (cuprous hydroxide or oxide) is formed. 



2. Cane-sugar. Perform Trommer's test with a sample of a solu- 

 tion. A blue liquid is obtained, which is not changed on boiling. 

 Now put the rest of the solution in a flask. Add o^th of its bulk of 

 strong hydrochloric acid, and boil for a quarter of an hour. Again 

 perform Trommer's test. Remember that excess of alkali must be 

 present after the acid is neutralized. The test now shows much 

 reducing sugar. The cane-sugar has been ' inverted ' i.e., changed 

 into a mixture of dextrose and levulose. 



3. Starch. (i) Cut a slice from a well- washed potato ; take a 

 scraping from it with a knife, and examine with the microscope. 



