135 



Nemertiue des Genfer Sees , auch hier in allen Merkmalen mit jener 

 vollkommen übereinstimmend, in einem Sumpfe nicht selten vor- 

 kommt. 



Basel, 2. März 1894. 



II. Mittheilungen aus Museen, Instituten etc. 



1. A new and easy method for bleaching animals and microscopical 

 sections fixed with osmio mixtures. 



By Dr. D. Carazzi, of the Spezia Civic Museum. 



eingeg. 12. Februar 1894. 



For the purpose of getting rid of the blackening that occurs in 

 animals and microscopical sections , as a consequence of treatment by 

 osmic mixtures, Paul Mayer and Marsh have found the well known 

 »chlorine method«. But the objects are required to remain in acid 

 liquid, and heat is often necessary for evolving chlorine; at last, the 

 chlorine appears to have an injurious effect on the tissues. 



These inconvénients are avoided by the »oxygenated-water me- 

 thod«. The peroxide of hydrogen , H°0°, becomes reduced at contact 

 with organic matter, and this is bleached by the O at the statu nas- 

 centi. This is undoubtedly a valuable method, but the oxygenated 

 water is very instable, and in a short time H"0° is converted in H^O. 



The difficulties are very perfectly got over by my »Peroxide-of- 

 sodium methodff. The compound has the formula Na^O^ and is a 

 yellowish powder; when put in water it evolves O, and the liquid 

 becomes alkaline, Na^O^ being reduced at Na^O, and Na^O + H^O = 

 2 NaHO (caustic soda). But if the water is mixed with acid the liquid 

 remains neutral, because the soda combines with the acid. 



You must not put large quantities of peroxide in a small quantity 

 of water, nor take mineral acids. If these precautious be not observed 

 a very violent reaction is set up, the evolving of O is very strong, 

 and molecules of powder are thrown all around. 



The acids more convenient for use are tartric and acetic. For 

 bleaching the objects I suggest the following method : A solution of 

 tartric or acetic acid (10 per cent.) is put in a vessel for animals, and 

 in a test-tube for microscopical sections; sink small quantity of the 

 peroxide, add slowly alcohol 70 per cent, at the surface of the water; 

 put in the alcohol the objects (which are before in alcohol). The O 

 escapes from the water, rises quickly to the level of separation of 

 the two liquids and dissolves in the alcohol slowly, bleaching the 

 specimen. 



La Specia, Civic Museum, 4. Febr. 1894. 



