COAL-TAR AK"D 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 first 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 
surplus 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 aluminum 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 applied to creosote to 
so great an extent as 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 (51) 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 sodium hydroxide having a specific gravity of one and fifteen hundredths (1.15) is 
added, is warmed slightly and placed in a separatory funnel. The mixture is 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 third 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 
