14 BULLETIN" 314, U. S. DEPARTMENT OF AGRICULTURE, 



The needle should be removed and thoroughly cleaned by wiping 

 with a dry cloth, after which it is ready for another test, The point 

 of the needle should be examined from time to time with a magnifying 

 glass to see that it is not injured in any way. If it is found defective, 

 it may be removed by heating the brass rod and withdrawing with 

 pliers.. A new needle may then be inserted in the heated brass rod, 

 and held firmly in place by a drop of soft solder. 



USE OF PENETRATION TEST. 



This test is made on all semisolid and solid oil-asphalts, asph&ltic 

 cements, and native asphalts, but seldom on tar products. It is 

 also often made on the residues of materials subjected to the volatiliza- 

 tion tests, when they are sufficiently hard. For work on residues, 

 which seldom amount to more than 20 cubic centimeters, a small 

 container, which. should not, however, be less than 1 inch in diameter, 

 will be required. 



While the standard conditions under which this test is made call 

 for a 1 00-gram load applied for five seconds on the material main- 

 tained at a temperature of 25° C, it is sometimes desirable, when 

 very soft materials are tested, to make the test with a 50-gram 

 weight. In order to ascertain how susceptible a material may be to 

 temperature changes, tests may be made at any other desired tem- 

 peratures, preferably 0° C, with a 200-gram weight for one minute, 

 and at 46° C. with a 50-grarn. weight for five seconds. 



In all cases the results of tests should be reported in hundredths 

 of a centimeter, as follows, showing all the conditions in order that 

 no misinterpretation of results may occur: 



Penetration ( seconds, grams at ° C.)= . 



MELTING POINT DETERMINATION. 



EQUIPMENT 



1 iron tripod. 



1 Bunsen burner and rubber tubing. 



1 piece of wire gauze 10 centimeters square. 



1 800 cubic centimeter Jena glass beaker, low form. (Fig. 8-a.) 



1 400 cubic centimeter Jena glass beaker, tall, without lip. (Fig. 8-6.) 



1 iron ring support (ring 7.5 centimeters in diameter) and burette clamp. (Fig. 8-c.) 



1 metal cover. (Fig. 8-d.) 



1 object glass. 



1 piece of wire (No. 12 Brown & Sharpe gauge) 20 centimeters in length, bent. (Fig. 



8-e.) 

 1 chemical thermometer reading from 0° 0. to 250° G. 

 1 cubical brass mold. (Fig. 8-/.) 

 1 large metal kitchen spoon. 

 1 steel spatula or kitchen knife, 



