ON PRESERVATIVE FLUIDS. 279 



ingredients are to be well stirred, and the solution very finely 

 filtered. These proportions form a strong fluid, but, if neces- 

 sary, a much larger quantity of water may be added without 

 any diminution of its preservative qualities. Another kind 

 consists of three pounds and a half of bay salt, seven grains of 

 corrosive sublimate, and six quarts of water; this fluid, from 

 containing no alum, is not so liable as the former to act on 

 Huch structures as shell and bone. Another kind, called the 

 arsenical solution, is made by mixing together two drachms of 

 arsenious acid, three pounds of bay salt, and six quarts of 

 water; to dissolve the arsenic, it should be boiled with a 

 portion of the water in a tin saucepan. All the above fluids 

 should be carefully filtered before they are used. 



Solution of Creosote. — Creosote does not readily mix with 

 water, but if in a very minute state of division it may be 

 suspended in it : one way of getting a solution is to mix it 

 with water in a retort and distill, the water will come over 

 highly charged with it. One objection, however, to the use of 

 this solution is its tendency to quit the water and adhere as 

 a deposit to the sides of the vessel in which it is contained. 

 Mr. Thwaites, of Bristol,* recommends a fluid into which 

 creosote enters as an ingredient for the purpose of mounting 

 preparations of algte ; it is made as foUows : — 



Mr. Thwaites^ Fluid. — To sixteen parts of distilled water 

 add one part of rectified spirits of wine and a few drops of 

 creosote, sufficient to saturate it, stir in a small quantity of 

 prepared chalk, and then filter : with this fluid mix an equal 

 measure of camphor-water (water saturated with camphor), 

 and, before using, strain ofl" through a fine piece of linen. 



For the same purpose Mr. Ealfs recommends the following, 

 viz., bay salt and alum of each one grain, to be dissolved in an 

 ounce of distilled water. Mr. Ealfs also informs us,t that 

 Mr. Sidebotham employs distilled water alone for mounting 

 delicate specimens of algae, and when the last coat of cement 

 is nearly dry, he applies a fine bronze with a camel's-hair 

 pencil. 



* Kalfs' Desmidiece, page 40. 

 t Op. at., page 42, 



