POTASSIUM 15 



PROCEDURE 



1. Subject tissue to freezing-drying (see page 3). , 



2. Transfer to paraffin, infiltrate in vacuo for 10-15 min. at 

 not more than 60°, and embed. Care should be taken to prevent 

 condensation of moisture on the dried tissue during the transfer 

 from the vacuum vessel to the paraffin. 



3. Cut 15 fjL sections using no water or ice, mount near edges of 

 large chemically clean cover slips, press down with finger, melt 

 paraffin with a tiny flame, and press down again. 



4. Remove paraffin by immersing the cover slips with the sections 

 in dry petroleum ether in a watch glass heated on a warm bar. 

 (Keep watch glass covered by another at all times except during 

 actual use. Replace the petroleum ether often.) 



5. Remove from petroleum ether and burn off excess quickly. 

 Allow to cool. 



From this point on, the test is carried out entirely in a cold room 

 the temperature of which should be 0° ± 1° during the manipula- 

 tions. All instruments and reagents are kept in this room. The 

 crystals of sodium potassium cobaltinitrite are relatively soluble at 

 room temperature, hence the precautions to maintain cold. 



6. When cover slips with sections are cold, cover each section 

 with a drop of the sodium cobaltinitrite solution. 



7. Drain off the solution and replace with glycerol. 



8. Mount on clean slide with section between slide and cover 

 slip. 



9. Examine under microscope with oil immersion lens. (Light 

 mineral oil is substituted for cedar oil since the latter is too viscous 

 at 0°.) 



Result. Short yellow rods with rounded ends in a diffuse pale 

 yellow background are the crystals of sodium potassium cobalti- 

 nitrite. 



Carere-Comes Siena Orange Method for Potassium 



SPECIAL REAGENTS 



Siena Orange Solution. Aqueous sodium p-dipicrylamine (prepared 



ready for use by K. Hollborn & Sons) . 

 10% Hydrochloric acid, p 



