186 Report of the Department of Botany of the 



Similar spotting of potato tubers results from exposure to the 

 fumes of ammonia, bromine or ether, and from dipping or soaking 

 in strong solutions of corrosive sublimate and formaldehyde. How- 

 ever, in the use of formaldehyde solution the quantity of potatoes 

 treated has no appreciable influence on the degree of the injury. 

 The same solution may be used at least ten times without loss of 

 strength. 



Rome, and some other varieties of apples, when injured by for- 

 maldehyde gas show, chiefly, lenticel spotting, while on Baldwin 

 the injury usually appears as a browning of the skin resembling 

 scald. 



ORIGIN AND DEVELOPMENT OF THE FORMALDEHYDE 



GAS TREATMENT. 



The germicidal properties of formaldehyde solution were discovered 

 by Loew 1 in 1888. During the next decade it came into wide use 

 as a disinfectant and antiseptic. 2 Its use on seed potatoes as a 

 preventive of scab (Oospora scabies Thax.) originated with Dr. 

 Arthur 3 of the Indiana Experiment Station in 1897. The method 

 of treatment which he recommended is widely used and everywhere 

 recognized as the standard. Simultaneously with the rise of formal- 

 dehyde solution as a disinfectant there came the use of formalde- 

 hyde gas for similar purposes. Being non-poisonous and harmless 

 to metals and fabrics it soon became popular for the disinfection of 

 rooms in which cases of contagious disease had occurred. 4 Several 

 methods of generating the gas were employed. In 1904, the discovery 

 of an improved method, called the formalin-permanganate method, 

 was announced by Evans and Russell. 5 This consists in pouring 

 a solution of formaldehyde over crystals of potassium permanganate. 

 In the resulting chemical reaction a large amount of formaldehyde 

 gas is liberated in the course of a few minutes. The chief merits 



'Loew, O. Physiologische Notizen uber Formaldehyd. Ber. Gesell. Morph. u. 

 Phys. zu Miinchen, 1888. 



2 For the literature of this period see the bibliography appended to Arthur's paper 



in Ind. Sta. Bui. 65. 



3 Arthur, J. C. Formalin for prevention of potato scab. Ind. Sta. Bui. 65. 1897. 



4 The literature of formaldehyde disinfection prior to 1901 has been collected by 



Reischauer (Hyg. Rundschau 11: 636). 



5 Evans, H. D. and Russell, J. P. Formaldehyde disinfection. Me. State Bd. 



of Health Rpt. 13. 1904. Reprint. 



