17 



LIST OF USEFUL CHEMICAL EEAGENTS. 



Acetic Acid, glacial (see " Corrosive Sublimate "). Only a 

 Very small quantity of this will be required. Its use is to 

 counteract the shrinkage of tissues, caused by solutions containing 

 corrosive sublimate. A few drops added to the solutions are 

 sufficient 



Alcohol. The l)est is " pure spirit," which can often l)e 

 obtained more easily abroad than in England, where the heavy 

 duty makes its price almost prohibitive. For 

 export only it may be obtained from English 

 firms at about 2s. 6d. per gallon, or 10s. for a 

 10-gallon drum (returnable). The strength of 

 the spirit as purchased should be about 90 per 

 cent. For most purposes a strength of 70 

 per cent, is sufficient for use ; this is obtained 

 by adding 70 volumes of the 90 per cent, 

 spirit to 20 volumes of water. Similarly, a 

 50 per cent, solution is obtained by diluting 

 50 volumes of 90 per cent, spirit with 40 

 volumes of water 



Ordinary " methylated " spirit can be used 

 for some animals, but cannot be diluted, as a 

 white precipitate is formed on addition of 

 water. For delicate marine animals it is 

 quite useless. What is known as Industrial 

 methylated spirit is, however, suitable for 

 j)reserving specimens. In England it can 

 only be obtained by special permit from the 

 Customs authorities, and only in considerable 

 quantities. 



Sudden changes in the strength of this 

 reagent should be avoided. Thus if it be 

 desired to transfer specimens from corrosive 

 sublimate to alcohol, they should be placed, 

 after washing with water, in a weak solution 

 of alcohol before being transferred to stronger 

 spirit. 



Chloeal Hydrate (Crystals), used for 

 narcotizing certain kinds of worms (e.g. 

 Nemertines) before killing them, so as to 

 cause them to die expanded. A few of the 

 crystals may be added to the sea-water, or the animals may be 

 placed in a 1 per cent, solution of the substance made up in sea 

 water. Further remarks about narcotizing are made on page 21. 



FKU'RE 17. 



Ptychodera minuta, 



enlarged about Ij 



diameters. lENTERO- 



PNEUSTA.l 



