326 A. M. Mayer — Determination of the coefficient 



ice, and when the level of the water in the tube has remained 

 stationary for 15 minutes it is marked by pasting on the tube a 

 piece of thin tracing paper on which is drawn in ink a very fine 

 line. This line is made tangent to the meniscus of the water by 

 the aid of a cathetometer. The ice is now replaced by cold water 

 which is slowly heated. When the temperature had reached 

 8° C. the volume of water (in this special apparatus) had fallen 

 11 cms. below the level it had at 0°. It then slowly rose till at 

 15°"9 C. it reached the level it had at 0°. The temperature of 

 the air of the room was above 15° 9. When the water was 

 raised to 12° it was allowed, under constant agitation, slowly 

 to reach 15° 9. To be sure that this was the temperature of 

 the water inside the vessel the water outside was kept at this 

 temperature by adding from time to time small portions of cold 

 water. The water level remained the same for 10 minutes. 



Referring to a curve of absolute expansion of water (drawn 

 to the scale of 1 mm. = yo oVoo" °^ un ^ °f volume) we find that 

 the ordinate of 15° - 9 is 1 '000653, which is the cubical expan- 

 sion of the brass caused by heating it from 0° to 15° # 9, and 

 •000853 divided by 15° -9 gives -00005364 the coefficient of 

 cubical expansion of brass of the following composition : cop- 

 per, 78'5 per cent; zinc, 21'05 ; lead, 25; tin, 0"15. 



The delicacy of the method depends on the relative dimen- 

 sions of the vessel and tube. In the apparatus just described 

 the interior diameter of the vessel is 6'147 cms ; its length 

 254 cms; the bore of the tube is *203 in diameter; hence 



X 25-4 -=- 1000 = 23-589, the length in cms. that the 



203 s 



level of the water changes for a change of lo 1 o0 in the volume 

 of the cylinder, and a change of Tirawfro" °^ tn - e volume equals 

 •023 cm., or -23 mm., of motion of water in the tube. From 

 the curves of apparent expansion of water in vessels of the 

 following named materials we find that a change of o- 10 in 

 the water at the temperature when the water has the same 

 apparent volume as at 0° equals a change of volume given 

 opposite the respective materials forming the vessels as follows : 



± 0°*1 C. causes a change of apparent volumes of "000008 in a glass vessel. 



" " " " -000009 " steel " 



" " " " -000010 " copper " 



" " " -000011 " brass " 



" " " " -000013 " zinc " 



From above data we compute that with a cylinder, or bulb, 

 and tube of the same dimensions as those of the brass vessel 

 and tube described, 



± 0°1 C. causes a motion of 1 '84 mm. in a similar vessel of glass. 

 " " 2-07 " " steel. 



" " 2-30 " " copper. 



" " 2-53 •' " brass 



" " 2-99 " " zinc. 



