JACKSON AND PHINNEY. PICRYLMALONIC ESTER. 105 



only the stable form melting at 64°. Crystallizations of the form 

 melting at 5S° gave, after the work had been in progress some time, 

 the form melting at 64°. We then crystallized a specimen melting 

 at 58° in a fresh room, which had not been used for these experi- 

 ments, and obtained in this way the rectangular plates melting at 58° ; 

 but upon recrystallizing the specimen, the form melting at 64° appeared, 

 and after this the first crystallization of a fresh specimen melting at 58° 

 in this room gave crystals of the form melting at 64°. A probable ex- 

 planation of these latter observations is that there was a little dust of 

 the more stable modification in this room coming from the clothes of one 

 of us, who used it as a lecture room, and that this was sufficient gradually 

 to inoculate the solutions. As the laboratory building, apparently con- 

 taminated with the dust of the more stable form, seemed to offer little 

 chance of preparing more of tlie form melting at 58°, we postponed pub-- 

 lishing this paper for some years, in the hope that one of us (who left 

 Cambridge at the end of the year) might prepare more of the form melt- 

 ing at 58° by working in entirely new surroundings. Unfortunately, the 

 pressure of other duties has prevented the carrying out of this work, 

 and we have decided that it is wiser to publish now the results already 

 obtained rather than to postpone the appearance of the paper to a still 

 later date. 



The conversion of the form melting at 58° into that melting at 64° 

 has been brought about by us in the following ways. By its conversion 

 into the ammonium salt and setting free the ester by acidification ; * by 

 inoculating a saturated alcoholic solution with a crystal of the form melt- 

 ing at 64° ; by melting the less stable form it was partially changed into 

 that melting at 64°, and, if the melting was repeated, the change became 

 com[)lete. It is possible, however, that this change might have been due 

 to inoculation from dust. On the other hand, we have not succeeded in 

 converting the form melting at 64° into that melting at 58° in s[)ite of 

 many experiments ; even melting the more stable form and stirrinaf it 

 with a rod tipped with the modification melting at 58° did not have the 

 desired effect. 



The substance melting at 64° was purified by crystallization from alco- 

 hol, and after being dried in vacuo was analyzed with the followino- 

 results : — 



I. 0.2050 gram of the substance gave on combustion 0,3149 gram of 

 carbonic dioxide and 0.0736 gram of water. 



* In my earlier work with Socli, the sodium salt yielded on acidification the 

 ester melting at 58°. — C. L. J. 



