ANILINE OIL-^BERLIN BLUE 287 



Aniline Oil. — Excellent for dehydrating sections, since it 

 will dissolve about 4 per cent, of water and may be kept dehy- 

 drated by a small piece of solid KOH which is insoluble in it. 

 The sections may be transferred from the aniline immediately 

 into Canada balsam. 



Aniline Sulphate. — Make a saturated aqueous solution. 

 As a test for lignified membranes mount the sections in the solu- 

 tion and add a drop of sulphuric acid, and a yellow color is 

 given to the lignified membranes. 



Or pour sulphuric acid slowly into aniline oil until a pre- 

 cipitate is produced throughout and then add water until the 

 precipitate is dissolved. This will not require the addition of 

 sulphuric acid to the sections. 



Balsam. — Canada balsam dissolved in xylol is, on the whole, 

 the best medium for making permanent mounts of sections 

 under a coverglass. For the method of doing this see page 

 265. Balsam in xylol can be obtained ready prepared of the 

 dealers. 



Barium Chloride. — This is sometimes used to distinguish 

 calcium oxalate from calcium sulphate. When barium chlo- 

 ride is run under the coverglass, calcium oxalate, if present, 

 is left unchanged, while a fine granular layer of barium sul- 

 phate comes to incrust any crystals of calcium sulphate. (2) 

 To determine the presence of tartaric acid, barium chloride 

 and antimonic oxide in hydrochloric acid is run under the cover- 

 glass, producing, with tartaric acid rhombic crystals of anti- 

 monium-barium-tartrate, whose obtuse angles measure 128°- 



Benzol. — Used in detecting caffeine, thus: Sections are heated 

 on the slide in a drop of distilled water until bubbles arise, 

 then the wa,ter is allowed to evaporate, and the residue is dis- 

 solved with a drop of benzol. The benzol is then allowed to 

 evaporate and the caffeine is .deposited on the edge of the 

 drop in the form of colorless needle-crystals. 



Berlin Blue. — Useful in the study of the growth in thickness 

 of the cell-membranes. In the study of marine algse — notably, 

 Caulerpa prolifera — it is used in the following manner : A vigorous 



