358 PRESERVATION OF MARINE ORGANISMS 



similar to that described above, excepting that after 

 using the sea water solution the washing in fresh water 

 should be more thorough. 



This is a most deadly poison if taken internally, and 

 a saturated solution looks exactly like plain water. 



Picric acid is a bright yellowish flaky powder, which 

 is scheduled under the Explosives Act. In a glass 

 bottle by itself there is good evidence that it is a 

 harmless substance, especially when kept under water, 

 but on the discharge near it of a detonator it becomes 

 a violent explosive. It is used in the manufacture of 

 bombs and shells, under the names of melinite, lyddite, 

 etc. The Board of Trade Regulations forbid its con- 

 veyance on board a ship (see p. in, note). 



Picric acid is often used for rapidly killing marine 

 animals, and is a good fixative, with a great penetrating 

 power. It may be either used alone or in combina- 

 tion with other chemicals. As a saturated solution in 

 water is always used, there is no trouble about making 

 up the stock solution. Simply place some picric acid 

 in a bottle and fill up with water. If clean fresh water 

 should not be available, then sea water may be used 

 instead. A little picric goes a long way, for one part 

 of picric dissolves in about eighty-six parts of water ; 

 but it is more soluble in hot water. 



There is one disadvantage with picric acid — namely, 

 the trouble of removing the yellow stain. After the 

 specimen has been properly fixed in picric, transfer it 

 to alcohol, and change the alcohol several times, until 

 the fluid is no longer yellow. It does not matter very 

 much about the specimen remaining yellow. To re- 

 move all traces of the stain from the specimen generally 

 takes several days and many changes of alcohol. 



