by Contact of Liquids with Powdered Silica Sfc. 311 



temperature increased with the strength of the solution ; but 

 those produced by strontium chloride in exps. 4, 27, and 33 

 do not appear to afford consistent results : whether this was 

 due to differences of molecular constitution of the dissolved 

 substance I have not investigated. 



Influence of Size of the particles of Silica. 



Exp. 59. — With 50 centim. of the 10-per-cent. solution of 

 potassium cyanide and 100 grains of coarse quartz sand, the 

 particles of which averaged about one sixteenth of an inch in 

 diameter, the rise of temperature was only *03 C. degree, 

 whilst that produced by the same w eight of the precipitated 

 silica was '82 C. degree (see exp. 57), or 27*3 times as much. 

 These results indicate a method of ascertaining the average 

 magnitude of the particles of insoluble powders. 



Alumina with various Liquids. 



In each of the following cases, 200 grains of alumina and 

 50 centim. of 10-per-cent. solutions of the substances were 

 employed. The alumina was precipitated from a solution of 

 alum by means of ammonia, then thoroughly washed, and 

 finally heated to redness, and was very pure. 



Table II. 



Exp. 



Cent. 

 Degrees. 



KHC0 3 * 50 



Am.SOi -54 



Exp. 



Cent. 

 Degrees. 



NaBr 1-70 



AmCl 1-76 



CdS0 4 1-86 



60. 

 61. 

 62. 

 63. 

 64. 

 65. 

 66. 

 67. 

 68. 

 69. 

 70. 



71. 



72. 

 73. 



74. 

 75. 

 76. 

 77. 

 78. 

 79. 

 80. 

 81. 



SrCl 2 -59 



Na.,C0 3 -74 



CdCl 2 1-38 



Na 2 S0 4 2-06 



KCy 107 



H 1-16 



MgS0 4 2-34 



K 2 C0 3 2-40 



CuS0 4 2-40 



KBr 2-45 



NaCl 2-58 



KCl 1-34 



ZnS0 4 1-55 



MgCl 2 1-64 



AmHO 1*64 



KNO3 1-66 



In every instance with alumina a rise of temperature oc- 

 curred : the probable explanation of this, however, is similar 

 to that with silica. 



Remarks. — Although a 10-per-cent. solution of common 

 salt produced so large a rise of temperature by contact with 

 alumina, it only lost 1*1 per cent, of dissolved substance (see 



Y2 



