AND HOW TO USE IT. 195 



syrup ; add i drop of sulphuric acid. The reaction produces a 

 purpHsh-red colour, if the substance contains either muscular 

 Tissue, corpuscles of blood, pus and mucus, epidermic and 

 epithelial scales, hairs, feathers, horn, whalebone, cellular parts of 

 algae, etc. The reaction is not produced in areolar, elastic tissue, 

 gelatine and chondrine, chitine, silk, cellulose, gum, starch, or 

 vegetable mucus. This is used as a test for cellulose, which it 

 colours blue. Dissolve zinc in hydrochloric acid, evaporate the 

 solution with excess of zinc until it acquires the consistence of 

 syrup, and dissolve in this enough iodide of potassium to saturate 

 it ; iodine is then added, and the solution diluted with water if 

 necessary. This reagent has the consistence of strong sulphuric 

 acid, and is of a pale yellowish brown. It must, of course, be 

 kept in a stoppered bottle. 



Carbolic Acid Preservative, for animal and vegetable tissues. 

 Carbolic acid, i drachm ; alcohol, 2 drachms ; distilled water, 

 1 2 ounces ; dissolve the carbolic acid with the alcohol, then add 

 it to the water and boil for ten minutes, and bottle for use. 



Acetate of Aluminium. — To i part of acetate of aluminium, 

 add 4 parts of distilled water. This is very good for preserving 

 vegetable colours, as in the case of desmids and other algae. 



Glycerine and Acetic Acid is useful for mounting many minute 

 insects and other objects ; it is composed of glycerine, i ounce ; 

 acetic acid, \ ounce. 



Siliceous Cement, for protecting corks from the fumes 

 of acid, etc. Mix together equal parts of colloid silica and 

 thick gum-water, with sufficient gilder's whiting to make it of 

 the consistency of treacle. 



Ralph's Liquid. — Bay salt, i grain ; alum, i grain ; distilled 

 water, i ounce ; dissolve and mix. This makes a good pre- 

 servative for many algae, etc. 



Spirit of Nitrous Ether (Sweet spirits of nitre) is much used 

 for delicate dissections of insects, and is made by a mixture of 

 sweet spirits of nitre and glycerine, in equal parts. 



For Labelling Slides. — A good plan is to punch some squares 



