APPENDIX A 253 



parts of turpentine are to be shaken well together, and set aside 

 till the cloudiness formed on their first mixing disappears. 

 V Cupric Hydrate. The ammoniacal solution of cupric hydrate 

 is used as a solvent for pure cellulose. To a solution of copper 

 sulphate in water add dilute potash : collect the precipitate on 

 a filter, wash with water, and then dissolve it in a little strong 

 ammonia : this solution, which is of a dark blue colour, must be 

 prepared fresh each time it is required for use. 



Dammar, dissolved in warm turpentine, and evaporated to 

 the consistency of syrup, is sometimes used as a mounting medium 

 instead of Canada balsam : it does not set so firmly as balsam) 

 and it is well to seal up slides in which it has been used. 



Ether is used as a solvent for wax, oils, &c. When very 

 small objects have been embedded in paraffin or cocoa-butter, 

 it may be convenient to dissolve off the fragments of embedding 

 material with ether : the small sections will then be readily found? 

 and collected. 



"Eau de Javelle " is recommended as a clearing agent for 

 growing points, and other merismatic tissues : the cell-contents 

 swell under its action, and the cell-walls which remain may then 

 be easily seen. It is prepared by adding to 2 pints of water 2 

 ounces of chloride of lime, and 4 ounces of carbonate of potash 

 or of soda. Objects treated with it are to be washed with 

 water, then with dilute acetic acid, and should be mounted in 

 glycerine. 



Eosin is used in strong solution in alcohol, or in water, for 

 demonstrating the structure of sieve-tubes. 



Fehiing's Fluid is used as a test for grape-sugar : the follow- 

 ing directions for its preparation are given in Foster's Practical 

 Physiology : 



a. Dissolve 34-65 grammes of pure crystallized cupric sulphate 

 in about 160 c.c. of distilled water. 



b. Dissolve also 173 grammes of pure crystallized potassic- 

 sodic tartrate in 600 to 700 grammes of sodic hydrate (sp. 

 gr. ri2). 



Add (a) to (), stirring well to cause a thorough mixture, and 

 dilute with distilled water to a litre. 



Fehling's fluid should be fresh made whenever it is required, 



