TESTS OP WOOD PRESERVATIVES. 11 



3 months the temperature of ignition was considerably raised, due 

 probably to the evaporation of the more volatile constituents. The 

 loss in weight from burning treated wood seasoned for 3 months was 

 also usually less than in the specimens burned shortly after 

 impregnation. 



In general, wood treated with oils ignited at lower temperatures than 

 wood treated with water-soluble preservatives. The temperature of 

 ignition in both cases was lower than that of untreated wood. 1 

 Furthermore, wood treated with oils showed in general greater loss 

 in weight after combustion than wood treated with the water-soluble 

 salts. It should be noted, however, that the amount of wood actually 

 burned may have been less than in the case of the salts. 



Untreated wood and wood treated with oils (exception, Timber- 

 asphalt) burned freely, and in general had to be extinguished after a 

 three-minute period, while wood treated with water-soluble salts 

 (exception, cresol calcium) burned slowly and became extinguished 

 in less than three minutes. 



TOXIC EFFICIENCY OF THE PRESERVATIVE IN INHIBITING FUNGOUS GROWTH. 



Table 5 2 contains the results of the tests thus far completed on 

 toxicity. The following conclusions on the toxicity of the various 

 preservatives should not be considered as absolutely final, because of 

 errors peculiar to the Petri-dish method. 



The products obtained from the high-boiling constituents of coal- 

 tar creosote, for example, the carbolineums and high-boiling creosote 

 fractions, were much less toxic than the coal-tar creosote or the low- 

 boiling fractions. The products with the greater toxic properties are 

 those having the lower specific gravities and lower boiling points. 



The same was true to an exaggerated degree in the water-gas-tar 

 creosotes, the 1.012 oil being about as toxic as coal-tar creosote, 

 while the 1.07 oil was only slightly toxic. 



The hardwood tar and Spirittine (from yellow pine) were less than 

 half as toxic as coal-tar creosote. Wood tar from Douglas fir and 

 Preservol were about equal to coal-tar creosote in toxicity. Beech- 

 wood creosote was more than twice as toxic as coal-tar creosote. 



Of the water-soluble salts tested sodium fluoride was the most 

 highly toxic, being from one and one-half to two times as toxic as 

 coal-tar creosote. Zinc chloride was slightly more toxic to Fomes 

 annosus, but far less toxic to Fomes pinicola than coal-tar creosote. 

 Cresol calcium was also very highly toxic, being from two to four 



1 Wood dipped in a 50 per cent sodium silicate solution ignited at a temperature of 448° C, and its weight 

 was reduced 17 per cent, although biirning immediately ceased when the sample was dropped in the lower 

 chamber ol the inflammability apparatus. 



' 2 This table was published in the Jour. Ind. and Eng. Chem., Feb., 1914, by C J. Humphrey and Ruth 

 Fleming, who conducted the tests. They are included here because they are an important factor in dete r- 

 mining the value of these preservatives. 



