60 



make wise the specification of an oil which shall contain as many as 

 possible of the constituents of an original distillate in sufficient amount 

 to make it representative of a whole oil, as far as it is possible to do so 

 without unduly restricting sources of oil supply or increasing the price. 

 This consideration has partly influenced the restoration of the naphtha- 

 lene clause formerly common in creosote specifications. With respect 

 to this, however, certain special considerations will be stated later. 



3. High residue content. 'The tendency of recent years to increase 

 the distillation temperature limits in the production' of creosote oil 

 may doubtless have produced beneficial results, within limits. Oils 

 have recently been received on the Pacific Coast, however, in which 

 analysis shows the proportion of residue above 355 C. to be in excess 

 of 50 per cent- In one authentic case it reached 59 per cent. Practical 

 experience in the conduct of the treating process seems to indicate 

 that with so refractory a wood as Douglas fir, an oil having such an 

 excessive residue increases the difficulty of securing penetration and 

 the danger of insufficient penetration. Such an oil would be accepted 

 by the standard specification of the Association. It is believed, there- 

 fore, that the amount of residue should be restricted, at least until its 

 value or lack of value shall have been demonstrated either by service 

 tests or by scientific investigation. 



The modifications herein presented respecting tar acids and the 

 limiting of residue, together with certain distillation limits then be- 

 lieved desirable, were referred to the Preservatives Committee of the 

 Association on July 29, 1921, and were approved by them for this pur- 

 pose. Certain further modifications have since appeared to be desira- 

 ble and are incorporated herein, as suggestions, from the trial of which 

 the ultimately desirable specification may be approached. The data 

 on which to base modification is in some cases manifestly meagre, 

 but it is hoped that experience with this tentative specification for 

 local application may contribute to the ultimate solution of the prob- 

 lem for all concerned. 



SAN FRANCISCO BAY MARINE PILING COMMITTEE 



TENTATIVE SPECIFICATION COVERING CREOSOTED DOUGLAS 



FIR PILING AND LUMBER FOR USE IN 



MARINE STRUCTURES 



(Adopted by the Committee, October, 1921.) 



MATERIALS TO BE TREATED 



Piling, Green and Water Stored 



Quality. Piles shall be cut from sound trees; shall be close 

 grained and solid, free from defects, such as injurious ring shakes, 



