UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 13, No. 3, pp. 39-42, 2 text figures April 14, 1914 



A NEW SELF-REGULATING PARAFFIN BATH 



C. W. WOODWOETH 



A very simple form of paraffin bath for imbedding tissue for the 

 microtome has been in use in my laboratory for several months and has 

 proven exceedingly satisfactory, being very convenient and maintain- 

 ing a uniform temperature. Many forms of thermostats had been 

 used by us in previous j^ears but this present apparatus is so much 

 more dependable that we have discarded other forms of thermo- 

 regulation for this. 



The present form of the apparatus is simply a glass flask about 

 one decimeter in diameter heated by vaporized chloroform. The neck 

 of the flask is a slender tube nearly a meter long, which ends above 

 in a thistle-tube funnel, for convenience in introducing the regulating 

 fluid. A small quantity of chloroform is poured into the flask through 

 the long neck. The heat from a sixteen candle power electric bulb 

 fills the flask with the vapor of chloroform at its boiling temperature 

 about 58° C, which is exactly right for the melting of the paraffin. 

 Since the tube of the flask is open to the air, the temperature within 

 cannot rise above that of the boiling point of the chloroform in air 

 which varies only slightly with the barometer. At high altitudes it 

 might be necessary to use a mixture of chloroform and carbon tetra- 

 chlorid to obtain the right temperature. 



If the source of heat varies the amoimt of vapor to be condensed 

 varies but not the temperature and it only warms up a greater or less 

 amount of the long vertical tube. All other forms of regulation for 

 paraffin baths known to us depend on differences in temperature of 

 the medium in the bath about the regulator to become operative. 



Practically all of the chloroform is condensed and flows back into 

 the flask. After months of use the level of the liquid is not appreci- 



'te-ral M^- 



