COAL-TAR AND WATER-GAS TAR CREOSOTES. 101 



Conical collar. — The conical collar shall be made of brass, and shall be of the form 

 and dimensions shown in figure 48. 



Place the brass collar with the small end on the brass plate, which has been pre- 

 viously amalgamated with mercury by fii'st rubbing it with dilute solution of mercuric 

 chloride or nitrate and then with mercury. Pour the residue to be tested into the collar 

 direct from the retort, as described in the paragraph on "Distillation" or heat it in a 

 tin box on water or steam bath, not by direct application of flame, and then pour into 

 the collar in any convenient way until slightly more than level with the top. The 

 81^1)1113 may be removed after the material has cooled to room temperature by means 

 of spatula or steel knife which has been slightly heated. Then place the collar and 

 plate in one of the tin cups containing ice water maintained at 5° C, and leave in this 

 bath for at least 15 minutes. 



Meanwhile, fill the other cup about three-fourths full of water and place on the 

 tripod; heat the water to any desired temperature at which the test is to be made. 

 This temperature should be accurately maintained, and should at no time throughout 

 the entire test be allowed to vary more than 0.5° C. from the temperature specified. 



After the material to be tested has been kept in the ice water for at least 15 minutes, 

 and not more than 30 minutes, remove the collar with its contents from the plate and 

 screw into the al umin um float, which is then immediately floated in the warmed bath. 

 As the plug of residue becomes warm and fluid, it is forced upward and out of the collar 

 until the water gains entrance to the saucer and causes it to sink. 



The time in seconds between placing the apparatus on the water and when the 

 water breaks through the residue shall be determined by means of a stop watch, and 

 shall be taken as a measure of the consistency of the material under examination. 



TAR-ACID CONTENT TEST. 



Of late years the tar-acid test has not been apphed to creosote to 

 so great an extent ^s formerly. It can not be used for identification 

 purposes, because tar acids may easily be added to products that 

 do not contain them, and such adulterations can not now be de- 

 tected. A mixture of 15 per cent of blast-furnace oil with 85 per 

 cent of certain water-gas-tar creosotes will pass the tar- acid test, 

 the specific-gravity test, and the distillation test for coal-tar creosotes. 



The method of determining the tar acids adopted by the National 

 Electric Light Association {31 ) is as follows : 



One hundred cubic centimeters (100 c. c.) of the total distillate to three hundred 

 and fifteen degrees (315° C.) to which forty cubic centimeters (40 c. c.) of a solution 

 of sodimu hydroxide having a specific gravity of one and fifteen himdredths (1.15) is 

 added, is warmed slightly and placed in a separatory funnel. The mixture ia vigor- 

 ously shaken, allowed to stand until the oil and soda solutions separate, and the soda 

 solution containing most of the tar acids drawn off. A second and thii'd extraction 

 is then made in the same manner, using thirty (30) and twenty (20) cubic centimeters 

 of the soda solution, respectively. The three alkaline extracts are united in a two- 

 hundred cubic centimeter ('200 c. c.) graduated cylinder, and acidified with dilute 

 sulphuric acid. The mixture is then allowed to cool and the volume of tar acids 

 noted. The results should be calculated to percentage of original oil. 



NAPHTHALENE TEST. 



The naphthalene test described by Mann (53) is not, so far as is 

 known at the Forest Products Laboratory, used in this country to 

 any great extent. It consists in determining the melting point of 



