104 BELL SYSTEM TECHNICAL JOURNAL 



nated with the fungicidal coating it is fundamentally a quantitative measure 

 of the amount of fungicide which diffuses into the agar from the impregnated 

 paper specimen. 



A third group of test procedures employs soil or soil suspension in con- 

 junction with the preservative materials. Here the soil furnishes an active 

 microbial culture and supplementary nutrients and nutrilites. The soil 

 suspension method has been described by Furry, and Zametkin^, 1943, and 

 the soil burial method by the American Society for Testing Materials. 



The techniques included in the first group are time saving, permit of 

 repUcation, and are readily dupHcated by other investigators. However, 

 the results in the agar-fungicide system do not apply to a cellulose-fungicide 

 system and are therefore a source of confusion resulting from their mis- 

 interpretation when so used. Agar-fungicide systems as originally de- 

 scribed by Richards are quantitative tests and have been used principally 

 for comparative toxicity studies. From such comparative studies attempts 

 to predict the behavior of a preservative in subsequent field tests have 

 been generally unsuccessful. Examples of the discrepancies between the 

 results from field and petri dish tests will be discussed later in this paper. 



In general, the second group of methods takes a longer time, and replica- 

 tion leaves much to be desired. Since the preserved material is the same 

 for laboratory and field tests, better agreement between field and laboratory 

 results should be obtained with the kolle flask-wood block method and 

 the A.S.T.M. fabric methods. However, the Signal Corps method for 

 testing fungicidal coatings used on electrical equipment is not a a true test 

 of the coating material per se. 



The third group of methods introduces a large number of variables through 

 the use of soil. Previously, replication of results and concomitant duplica- 

 tion by other investigators had been lacking, due to microbial activity, 

 physical properties, nutrient properties, and moisture variations of the soil. 

 However, during experimental work with termites, the author* made certain 

 observations on the various factors involved in the decay process. These 

 led to an intensive study of the problem resulting in the development of a 

 test method for wood preservatives which overcomes many of the limitations 

 of earlier methods. The soil burial method is a severe test of fungicide 

 treated material, and, with the modification to be discussed in this paper, 

 it is anticipated that the variables which cause non-uniformity of results 

 can be eliminated. The method is also evaluated by comparison between 

 the results obtained in the laboratory and those obtained from parallel 

 field tests. 



Rapid decay of wood in contact with soil was obser\'ed during an attempt 

 to establish experimental termite colonies in the laboratory (Leutritz^, 

 1939). Instead of becoming infested by the termites, nearly all the blocks 



