220 Journal of Agricultural Research voi.xx.No. 3 



week, or at most two weeks, the damp seed ceased entirely to give any 

 formaldehyde reaction. An odd reddish brown color resulted when 

 Tollen's reagent was added to these extracts, but there was no black 

 precipitate. The question was to determine where the formaldehyde 

 had gone, for it seemed extremely inconsistent that it should disappear 

 in a sealed jar and yet remain on seed open to the air. The answer was 

 suggested by Dr. C. W. Porter, organic chemist at the University of 

 California, who said that it probably was absorbed by bacteria and mold 

 growing in the damp wheat. 



To determine whether this were the case, some treated seeds were 

 divided into several lots. Part were inoculated with the spores of Penicil- 

 lium and sealed in small jars. The rest were left uninoculated and stored 

 similarly. Within a few days extracts of the former samples ceased 

 giving the formaldehyde reaction and produced the peculiar reddish 

 brown color noted above. The uninoculated lots continued to show the 

 presence of the chemical for some days longer but eventually became 

 moldy and then gave the same reddish brown color with the ammoniacal 

 silver nitrate. 



Having demonstrated the persistence of formaldehyde on drying seed 

 and its disappearance from seed stored damp, and having evidence 

 pointing to the fact that seed injury from this fungicide may be dependent 

 on the formation of paraformaldehyde on the seed, we next undertook a 

 more critical study of the evaporation and polymerization of formalde- 

 hyde solutions. 



It was found, upon evaporating the undiluted commercial solutions, 

 that a surprisingly large quantity of the solid, white, condensation product 

 was produced from comparatively small volumes. The percentage by 

 weight of the solid formed varied greatly in different determinations 

 because of variations in the conditions affecting the rate of evapora 

 tion — namely, quantity of solution, area of free surface, atmospheric 

 humidity, temperature, etc. Even with these factors controlled, the 

 same percentage could not be obtained with successive determinations 

 because there is continuous evaporation of the solid paraformaldehyde 

 after it has formed, as well as of the moisture in the, at first, waxy residue. 

 In our determinations a procedure as nearly uniform as possible was 

 always followed — that is, 50 cc. of undiluted 36.2 per cent formaldehyde 

 solution were evaporated by exposure to the air in a 100-cc. evaporating 

 dish, the residue being allowed to dry until the yellow color and waxy 

 texture had disappeared. The dry residue was weighed as soon as 

 possible after it became pure white, brittle, and easily powdered. A 

 solution analyzed at the Insecticide Laboratory of the University of 

 California and found to contain 36.2 per cent formaldehyde (specific 

 gravity 1.090) produced under these conditions an average of 9.85 gm. 

 of paraformaldehyde per 50 cc. This is 18.07 P er cent °f the weight of 



