Reagents and Processes. 385 



ing and Sealing in Balsam. By this process of staining the lignified 

 walls should be blue and the cellulose walls red. If a proper differ- 

 entiation is not obtained by the time ratios here given, a little experi- 

 mentation will show what the time ratios should be for the specific 

 material. 



Fehling's Solution for Demonstrating Grape Sugar (Glucose) . 

 Make three stock solutions, which are to be preserved in separate 

 bottles. 



1. 17.5 grams of copper sulphate dissolved in 500 cubic centimeters 

 of distilled water. 



2. 86.5 grams of sodium-potassium-tartrate (Rochelle salts) in 500 

 cubic centimeters of distilled water. 



3. 60 grams of sodium hydrate in 500 cubic centimeters of distilled 

 water. 



To prepare for use, mix I volume of each of the three stock solu- 

 tions with 2 volumes of distilled water; for example, mix 10 cubic 

 centimeters of each of the solutions with 20 cubic centimeters of water 

 (50 cubic centimeters in all). The mixture should have a clear blue 

 color. 



Place the material to be tested in the mixture in a test tube and boil 

 for a few moments. If glucose is present, a red or orange precipitate 

 of cuprous oxide will be formed. 



Glycerine Jelly. Soak for 2 hours 6 parts by weight of best 

 gelatine in 2 parts by weight of distilled water, and add 7 parts by 

 weight of pure glycerine. Add to each 100 grams of this i gram of 

 crystallized or concentrated carbolic acid. Warm the mixture over a 

 water bath and stir it until it is clear. Then strain it through filter 

 paper placed in a funnel in a steamer or incubator to keep the mixture 

 fluid enough for filtering. Wet the filter paper with distilled water 

 before pouring in the mixture. Keep the jelly well stoppered and free 

 from dust. 



This is an excellent mounting medium for microscope objects. Use 

 it as follows : Put a small piece of the jelly on a glass slip and slowly 

 warm the slip over the flame of an alcohol lamp, or other suitable flame, 

 until the jelly melts. Then place in the melted jelly the material to be 

 mounted, which has first been brought into concentrated glycerine as 

 directed under Safranin. Clean and warm a coverglass and carefully 

 place it over the preparation by standing it on one edge and gradually 

 lowering it so as not to entangle air bubbles. (See directions for doing 



