NOTES ON METHODS, AND SELECTED REAGENTS. 495 



For mounting in glycerine-jelly or Hoyer's fluid, water or alcohol must 



previously be removed by laying for some time in glycerine. 

 Preparations in acetate of potash retain their chlorophyll. 

 CLOSING. Preparations mounted in Glycerine-jelly, Hoyer's fluid, Canada 

 balsam, or dammar do not need further closing. In all these cases 

 it is however desirable to put one or two thin layers of 

 Gold-size with a fine brush, over the junction of cover-glass and object- 

 glass. This must not be done till the mounting-fluid has set firm ; 

 and one layer of gold-size should be dry before another is added. 

 Preparations in glycerine should be hermetically sealed with- Canada 

 balsam in turpentine, laid round the cover-glass thinly with a thin 

 glass rod, and, when dry, topped with gold-size. 

 Preparations in acetate of potash should be closed with gold-size. 

 LABELLING. Paper labels may be stuck on the object-slides with pure gum 

 containing a trace of glycerine or of aluminium sulphate, as described 

 in Appendix II. Card labels, on the other hand, with gla* cetn> ,<t. 

 such as Crystal Palace cement, coaguline, etc. 



The following is a still more restricted list, answering nearly all 

 practical purposes: 



MICRO-CHEMICAL REAGENTS. Potassium-iodide iodine, Chlor/inc iodine. 

 Sulphuric acid (cone.), Hydrochloric acid (cone.), Nitric acid (strong), 

 Acetic acid (2 per cent), Chromic acid (25 per cent.), Aniiiumi;i 

 (strong), Osmic acid (1 per cent), Caustic Potash, Perchloride of 

 iron, Chlorate of potash (crystals), Ether, Alcanna tincture, Carbolic 

 acid, 10 per cent. Sodium chloride solution. 



PRESERVING FLUID. Methylated alcohol (old style). 



FIXING AND HARDENING FLUIDS. Absolute alcohol, Chromic acid, 1 per 

 cent. 



CLEARING FLUIDS. Potash in alcohol, Eau de Javelle or Chloral hydrate, 

 Oil of cloves. 



STAINS. Methyl-blue, Corallin, Acetic gentiana-violet, Mayer's Carmalum 

 (alum carmine), Logwood, Safranin, Methyl-violet, Fuchsin iodine- 

 green, Eosin-logwood, Rosuniline violet. 



MOUNTING MEDIA. Glycerine, Glycerine-jelly, Canada balsam, Gold-si/e, 

 Gum, Acetate of Copper enclosing fluid for Algae. 



