. Canadian engineer. cific gravity multiply into very consider-able differences between what is shipped at one point andreceived at another, it is worthy of careful consideration. The temperature of bituminous materials affects prac-tically all of the physical tests to which they are subjected,and too much care cannot be exercised to insure thespecific temperature specified, being the actual conditionof the material under examination and not merely that ofthe surrounding air or water which may envelop it at thetime. This class of material absorbs and radiates heatslowly and the period of time
. Canadian engineer. cific gravity multiply into very consider-able differences between what is shipped at one point andreceived at another, it is worthy of careful consideration. The temperature of bituminous materials affects prac-tically all of the physical tests to which they are subjected,and too much care cannot be exercised to insure thespecific temperature specified, being the actual conditionof the material under examination and not merely that ofthe surrounding air or water which may envelop it at thetime. This class of material absorbs and radiates heatslowly and the period of time stated in a method, throughwhich a sample is to remain in water, or the procedure tobe followed in heating or cooling it, must necessarily bebased upon considerable experience in such matters andmust also be religiously followed if accuracy is important. While there may not be much room for honest dis-agreement upon the subject of specific gravity, there is nolimit to either the room for or the degree of disagreement. Fig. 1.—Improved Freas Oven for Losson Heating Test of Bitumens. in regard to practically all of the other tests to whichbituminous materials are submitted. Flash Point.—In addition to the dozens of miscellane-ous independent methods used for the determination of theflash or fire point, or both, there are as many as at leasteight more or less standard methods for the same pur-pose which may be described under the name of the ap-paratus used for the purpose. The eight standard methodsare as follows: Tagliabue, open and closed cup; NewYork State, closed cup ; Cleveland, open cup ; Abel, closedcup; Abel-Pensky, closed cup; Pensky-Martin, closedcup ; Bureau of Mines, closed cup. No open-cup method will yield results capable ofduplication in the hands of different operators, and thevalue of any results so obtained is questionable. The re-sults obtained under unlike conditions, either as to type orcup, or its manipulation, are not comparable. The closedcup tests can
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