:i20 tweNti-fuist jhu'ojit. 



tarring posts or boards in the greenhouse, or that more elusive type of trouble 

 which comes from painting steam pipes with certain tar-like paints, present an 

 interesting corroboration to the fact that fumes from tar do injure vegetation. 

 The method of approach of the problem in this paiier is different from that 

 of the other contributions reviewed in the above cursory literature survey. 

 The articles mentioned have been engaged in establishing the fact of injury 

 by Tar or "Tarvia" fumes. In this paper one of the many constituents of the 

 fumes has been tested as to its capacity for injury to plants. 



Attention was first drawn to the problem through the finding of some 

 inlvy-black apples in an express shipment in the fall of 1918. The very strong 

 phenol odor gave a clue to the cause of the discoloration. It was not possible, 

 however, to get the ordinary tests for phenol by crushing a piece of blackened 

 apple, and then testing the expre.ssed juice with iron salts. The textbooks 

 point out, however, that when the dilution of the phenol is too great to secure 

 results by color production, that the characteristic odor is sufficient. 



Believing, therefore, that phenol was responsible, attempt was made with 

 phenol fumes to reproduce the blackening. Concentrated phenol was placed 

 in a small battery jar, and apples were exi>osed to the fumes over night. By 

 morning, marked blackening was observed, not only of the skin but of the 

 flesh beneath. The appearance reproduced exactly that of the apples showing 

 the original injury. This preliminary test left no doubt as to the nature of 

 the trouble in the original apples. It seemed likely that in some way, doubt- 

 less through a broken bottle of chemical in an adjacent package, the apples 

 in the lower tier had been subjected to phenol fumes. 



The many experiments performed in testing phenol will not be considei-ed 

 in detail, since the methods were simple and largely consisted of exposure of 

 the fruit, placed upon supiwrts in liter battery jars with tight fitting glass 

 covers, to the fumes from various dilutions of plienol placed in the bottom of 

 the battery jar. When difl'erent temperature effects were tested the ordinary 

 laboratory Incubators were utilized. 



From experiments of the tyi»e indicated tlie following facts were estab- 

 lished : 



Blackening can be produced in from three to twelve hours by exposure of 

 the mature fruit of apples, pears, quinces, viiiifera graiMjs, plums, to the fumes 

 of phenol in dilutions so low as 1 or 2%. Certain vegetables were used and 

 and no consistent results were obtained, aside from the fact that potato 

 sprouts blackened quickly and sharply, but no effect was scon on the skins or 

 on the exposed flesh. 



The failure to secure the ordinary tests f«)r phenol indicated that the 

 chemical was present in an extremely small amount, hence a series of experi- 

 ments were undertJiken to find the minimum of phenol that would produce 

 blackening. Experiments were conducted with pieces of apple exposed to the 

 fumes of phenol given off by solution of various strengths. 



