72 



napthalene is one. The minimum limit of 10% for napthalene has been 

 selected after careful study of the analyses of a large number of oils. 

 It is possible to meet this requirement with any average grade of whole 

 oil. 



The probable value of napthalene in an oil for the preservation of 

 marine piling is increased by the observed fact that the rate of loss 

 of napthalene from treated wood submerged in water is very slow, in 

 contrast to its rapid loss from treated wood exposed in air. Whatever 

 value the napthalene has will therefore be longer effective in marine 

 work than in land work. 



Clause (L The analyses of a large number of oils used in the past 

 show that at least 50% distilled below 315 C., and that the residue 

 above 355 C. rarely exceeded 30%. This has determined the minimum 

 limits of 45% for the amount distilling below 315 C. and 70% for the 

 amount distilling below 355 C. The maximum limit of 90% for the lat- 

 ter rests upon the conclusion, as a result of our work, that some residue 

 above 355 C. is desirable to give stability to the oil, by minimizing 

 leaching. 



Clause 7 (second paragraph). There seems to be substantial 

 agreement in the industry that the specific gravity limit of 1.10 set, in 

 the standard specification, for the fraction between 315 C. and 355 C-, 

 is too high. It has often failed of fulfillment in practice. The limit of 

 1.09 herein specified has been selected after careful study of a large 

 number of oils, as permitting the use of the widest practicable number 

 of otherwise satisfactory oils, both domestic and foreign. 



Clause ;?. The specific gravity of the whole oil is largely deter- 

 mined by the requirements made for the several fractions. The dis- 

 tillation percentages required for the fractions in Clause 6 and the 

 specific gravities required for them in Clause 7 necessitate for the whole 

 oil a specific gravity of approximately 1.045, as specified. The large 

 number of records examined by the Committee do not indicate that any 

 large percentage of oils will be barred by this specific gravity. The 

 aim of the Committee has been to assure the users of creosoted material 

 for marine structures against defective oils, while on the other hand 

 to leave the field as open as possible to the producers of creosote oil. 



BIOLOGICAL SK( TK>\ 



By Charles A. Kofoid and Robert C. Miller 



The biological report for the present year is restricted to Teredo 

 i) aval in, including a brief statement of its action in San Francisco Bay 

 during 1921, a preliminary discussion of the factors limiting the per- 

 sistence and distribution of this borer in the bay with reference to sa- 



