INORGANIC SALTS. 37 



gm. ; potassic hydrate, 6 gm. ; pure glycerine, 7.5 

 cc. ; distilled water, 178 cc. 1 W. T.] 



Arabin (arabate of potassium) Cerasin (meta- 

 gummate of potassium) and Bassorin do not reduce 

 the Trommer reagent ; a dark blue precipitate only 

 is formed, the flocks of which unite into balls when 

 heated. 



Protein compounds are sometimes recognized by 

 the same tests, the contents of young cells 

 assuming a beautiful violet color, though older cells 

 fail to show the reaction. 



Cell-walls which are not lignified are colored 

 faintly blue by long soaking in an aqueous solution 

 of cupric sulphate. 



POTASH ALUM (Alum).* 



An aqueous solution 3 is employed as a mordant, 

 in various staining processes, e. g. in Frey's haem- 

 atoxylin and Grenacher's alum-carmine ; as an 

 anhydrating medium ; or, finally, as an aid in the 

 Hanstein method of clearing tissues, g. v. 



POTASSIC NITRATE (Niter, Saltpeter). 



This has been used in a one-fourth per cent, 

 aqueous solution as a culture-fluid for the living 



1 Wheeler : Organic Chemistry, p. 187. 



3 The ordinary commercial alum, which is ammonium-alum, is quite as 

 useful. 



8 Frey : Das Mikroskop, p. 93. Bachmann : Dauerpraparate, p. 28. 

 Hanstein : Scheitelzellgruppe, 1868. 



