48 



BULLETIiSr 1037, U. S. DEPARTMENT OF AGRICULTURE. 



terval of at least 14 inches was maintained between adjacent groups. 

 In the tile chamber the blocks were subjected to a temperature aver- 

 aging 80° F. and a relative humidity varying from 85 to 100 per cent. 

 At the end of three to four weeks all blocks were carefully examined. 

 The following observations were made at that time : 



Xone of the preservatives was entirely effective in controlling 

 mold when used in concentrations of 1 per cent. 



Blocks dipped in sodium carbonate, sodium bicarbonate, sodium 

 fluorid, sodium bifluorid, ammonium fluorid, magnesium silicofiuorid, 

 zinc silicofiuorid, and bleaching powder became badly molded. 



Potassium (alum), potassium chlorate, and copper sulphate seemed 

 to stimulate all or certain sj)ecies of the fungi used. The last seemed 

 to incite the growth of Aspergillus niger in particular. 





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Fig. 22. — Diagram illustrating the method cxf loading used by one of the large wheel fac- 

 tories and recommended by the wood-stock committee in connection with veliicle stock. 



Borax was effective in controlling the sap-stain fungus {Cerato- 

 stomeJla sp.) . Though it did not entirely prevent the growth of mold, 

 the amount of mold that did develop was very slight in comparison 

 with that on the blocks treated with the other preservative solutions. 

 Under these circumstances it compared favorably with 1 per cent 

 mercuric chlorid. 



The addition of the hygroscopic substances — sodium chlorid, cal- 

 cium chlorid, and glycerin — to the solutions of the preservatives 

 apparently did not increase their efficiency. 



Of the organic compounds and mixtures tested here, creosote in 

 kerosene gave the best results," while mykantin stood second. The 

 latter, however, stained the wood yellow, a property which would 

 prohibit its use for many purposes. 



