3l6 APPENDIX 2 



Make up the following fixatives in aqueous solutions at twice the 

 concentrations given on p. 24: — hydrochloric acid, nitric acid, 

 trichloracetic acid, chloroplatinic acid, chromium trioxide, form- 

 aldehyde, osmium tetroxide, potassium dichromate, acetic acid. 



Put 5 ml of the clear albumin solution in a test-tube and add an 

 equal volume of the fixative solution to be tested. (The experiment 

 may be done with smaller quantities when osmium tetroxide or 

 chloroplatinic acid is being tested, on account of the high cost.) 

 Close the tube and turn it upside down once. The fixative will 

 now be at the concentration shown on p. 24. 



Note the appearance of the contents of the tube immediately, at 

 5 min., and at i hour from mixing, and also on the following day. 

 Record whether there is opalescence, flocculation, or clot- 

 formation, and whether fiocculi or clots fall to the bottom of the 

 tube. 



A different technique is necessary with fixatives that are used in 

 practice at or near saturation or unmixed with water; namely, 

 picric acid, mercuric chloride, methanol, ethanol, and acetone. To 

 test these, mix egg-white with twdce its volume of water and clear 

 the solution by centrifuging. Put 3 ml of this stronger albumin 

 solution in a test-tube and add 7 ml of the fixative at the concentra- 

 tion shown on p. 24. It will be noticed that the amount of 

 albumin in the tube is the same as in the experiment described in 

 the preceding paragraphs. Close the tube and turn it upside down 

 once. Record the result as before. 



The results of these experiments are briefly recorded on p. 32. 



The coagulation of egg-albumin by ferric sulphate 



Add to egg-w^hite 4 times its volume of distilled water. Centrifuge 

 to clear. 



Put 5 ml of the albumin solution in each of two test-tubes 

 marked A and B. 



Make these solutions : — 



A. Ferric sulphate, anhydrous, 2% w/v aq. . . 2-5 ml 

 Distilled water. . . . . . . 2-5 ml 



B. Ferric sulphate, anhydrous, 2% w/v aq. . . 2-5 ml 

 Ammonium sulphate, 5-28°o w/v aq. . . . 2-5 ml 



Add solution A to test-tube A; close; turn upside down once. 

 There is only a momentary formation of a few specks of coagulum : 

 they dissolve at once. 



Add solution B to test-tube B; close; turn upside down once. 



