APPENDIX. 493 



b. Prepare a saturated solution of alum in 70 per cent, 

 alcohol. Add i volume of <2 to 8 of b. 



c. To the mixture of a and b add a few drops of a 

 saturated solution of pure haematoxylin in absolute 

 alcohol. 



d. Filter. 



This reagent stains with great intensity. Overstain- 

 ed preparations may be clarified by immersion for 

 a longer or shorter period in acidulated alcohol 

 (70 per cent, solution plus "25 per cent, solution of 

 nitric acid). 



13. Haematoxylin-ammonia, Solution of. 



Expose some crystals of Haematoxylin under a bell-glass 

 to the action of the Ammonia gas given off from a strong 

 solution. The crystals can then be dissolved in distilled 

 water. This reagent must be prepared fresh when re- 

 quired. 



14. Iodine, Solution of. 



Prepare a saturated solution of potassic iodide in dis- 

 tilled water; saturate this solution with iodine. Filter. 

 Dilute to a brown sherry colour. 



It sometimes happens that the iodine and sulphuric 

 acid tests for starch and cellulose fail, when dealing with 

 fresh material. Under such circumstances a check ex- 

 periment should be performed, as follows, viz. : — preserve 

 in alcohol, transfer to weak solution of caustic potash 

 for 6 — 8 hours, neutralize with dilute acetic acid and 

 finally stain, as in ordinary, with iodine and strong sul- 

 phuric acid. 



The presence of starch or cellulose should never be 

 denied before both the above-named tests have failed. 



1 5. Magenta, Solution of. 



Dissolve I decigr. of crystallized magenta (roseine) in 

 160 cubic centimetres of distilled water: add i cub. cent, 

 of absolute alcohol. Keep in a well-closed bottle. 



