222 



Journal of Agricultural Research 



Vol. XX, No. 3 



washings of the formaldehyde dishes, while the controls remained color- 

 less. This showed that paraformaldehyde is left as a residue on the 

 evaporation of solutions as weak as o. i per cent. 



By successive weighings of the same sample it was found that para- 

 formaldehyde is volatile, gradually breaking down and escaping as 

 formaldehyde gas. To this property we may safely look for a large part 

 of the seed injury following treatment with formaldehyde. Figure i 

 illustrates graphically the rate of decreasing weight of 10.54 g m - °f para- 

 formaldehyde exposed to the air of the room in an 8-cm. evaporating 

 dish in which it was originally formed by the evaporation of 50 cc. of a 

 36.2 per cent solution. 



r/ME /A/ WEEKS 

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Fig. i 





—Graph showing rate of evaporation of paraformaldehyde at room temperature, approximately 



ao"C 



INJURIOUS EFFECT OF PARAFORMALDEHYDE ON SEEDS 



After it had been demonstrated that a solid residue is left upon the 

 evaporation of a formaldehyde solution and that this substance is con- 

 stantly breaking down to form formaldehyde gas, it seemed probable that 

 the cause of injury to treated seeds upon drying was the production of 

 an atmosphere of concentrated gas adjacent to the seed as a result of the 

 constant evaporation of this coating of paraformaldehyde. The gas, 

 being heavier than air, would tend to remain around the seeds, especially 

 when they are dried in heaps so that diffusion is not rapid. This idea 

 was borne out by the results of an experiment showing the deleterious 

 effect on the seed of contact with the dry, powdered, paraformaldehyde. 

 Dry, untreated seeds were put in Syracuse watch crystals and covered 

 with powdered paraformaldehyde which was packed closely around them. 

 The watch crystals were left uncovered and placed in a dry place. At 



