236 PROCEEDINGS OF THE AMERICAN ACADEMY. 



crystals were transferred, after washing with absolute ether, to a 

 desiccator and allowed to dry in a stream of hydrogen. Some of 

 the salt thus prepared was submitted to analysis. All the operations 

 with this substance must be carried on as quickly as possible, since it 

 has a strong tendency to decompose, forming a black mixture, and 

 this change takes place even in vacuo or in an atmosphere of hydrogen, 

 although not so quickly as when in contact with the air. Even during 

 the weighing in a closed tube, the substance often decomposed, but the 

 following analyses were made with the unchanged substance, although 

 in all the analyses made the samples used were light brown in color, 

 showing that slight decomposition had taken place. 



I. 0.1357 gram of the salt gave 0.0396 gram sodic sulphate. 

 II. 0.1398 gram of the salt gave 0.0416 gram sodic sulphate. 



Calculated for Found. 



C 6 HBr 3 (ONa), . 2 C 2 H 5 0H I. II. 



Sodium 9.52 9.45 9.64 



These results indicate that the salt contained two molecules of alcohol 

 of crystallization, and that alcohol was present in the body was evident, 

 for a great many times, in attempting to weigh it, the contents of the 

 weighing tube would suddenly turn black, giving off heat, while a 

 liquid collected in large drops on the sides of the tube which was 

 recognized as alcohol. 



Properties. — The sodium salt of tribromresorcine crystallizes in 

 short flat prisms of a white color and a silky lustre. Its most strik- 

 ing property is its great instability, decomposing rapidly with the elim- 

 ination of alcohol, the salt becoming black in color; when dissolved 

 in water, the solution immediately turns black. A freshly prepared 

 lot of this sodium salt was divided into two portions, one of which 

 was put into a small tube through which a rapid stream of hydrogen 

 was passing, the other was put into a test tube which was surrounded 

 by a freezing mixture of salt and ice, the substance in the test tube 

 beinsf in contact with the air. It was found that the sodium salt in 

 the stream of hydrogen (at ordinary temperature) blackened more 

 rapidly than did the salt which was in the freezing mixture in contact 

 with the air. This experiment proves that the salt is more stable in 

 the cold than at ordinary temperatures, and also that the blackening 

 is not due to oxidation. Since then we had proved that this behavior 

 was not due to oxidation, it seemed possible that the black mixture 

 obtained by drying at 100° might have the same percentage com- 

 position as the dried salt. Accordingly the amount of sodium was 



