APPENDIX IV. 

 GENERAL NOTES ON METHODS, AND SELECTED REAGENTS. 



THE following notes include the most useful of the reagents given in 

 Appendix III., and those therefore which it is desirable should be included 

 in a limited selection. They are classified according to. their purpose or 

 nature. 



For alcohol and methylated spirit, see a note at the beginning of 



Appendix III. 



MICRO-CHEMICAL REAGENTS. These are used on account of certain effects 

 (reactions) which they produce upon some constituent or other of 

 the plant, and by which therefore the presence and nature of that 

 constituent can be recognised. Naturally in micro-chemistry we 

 are restricted to optical reactions, and hence these reagents always 

 produce distinctive effects, either swelling, dissolving, colouring, 

 evolution of gas, etc. 



(1) Iodine in alcohol. 



(2) - in glycerine. Can generally be made from (3) when re- 



quired. 



(3) Potassium-iodide iodine. 



(4) Chlorzinc iodine. 

 Acids. 



(5) Sulphuric acid (concentrated}. 



(6) - (dilute}. Can be prepared from (5) as required br 



mixing 1 drop with 1 or 2 of water. 



(7) Hydrochloric acid (concentrated). 



(?A) (| per cent, in 70 per cent, alcohol). 



7A can be prepared when wanted by putting 1 drop strong 

 acid in a watch-glass of 70 per cent, alcohol. 



(8) Nitric acid (strong). 



(9) Acetic acid (glacial). 



(9A) (2 per cent). Stock solution for fixing fluids. 



(10) Chromic acid (saturated). 



(10A) (25 per cent.). Other percentages can be made from. 



this as required. 

 (10s) - (1 P er cent.). Stock solution for fixing fluids. 



(11) Osmic acid (2 per cent). Stock solution for fixing fluids. 



(12) Picric acid. Saturated watery solution. 



(491) ' 



