6 AET. 8. S. KAWAMURA : COAGULATION OF COLLOIDAL 



comenic and hemipinic acids all coagulate the solution ; but their 

 exact power has not be ascertained. 



" The acetic, formic, boracic, arsenious, and cyanuric acids 

 do not coagulate, at least when moderately concentreted 



" The alkalies have a strong coagulating power. About 2 

 equivalents of potash produce an effect equal to 1 of sulphuric 

 acid, and the same is the case with soda, ammonia, and lime. 

 The coagulation takes place before the acetic acid which remains 

 in the aluminous solution is fully saturated ; for when the alkali, 

 in a very dilute state, is added with caution, the coagulum which 

 it produces has still an acid reaction. This coagulum, like that 

 from sulphuric acid, is insoluble in any acid, whether cold or 

 hot, as well as in pure water. It dissolves, however, in a boiling 

 solution of potash or soda, and when the alkaline solution is 

 afterwards saturated by an acid, the ordinary terhydrate of alumina 

 is thrown down. 



" Large quantities, however, of the acetic salts (ready formed) 

 may be added before they coagulate the aluminous solution. 

 When the solid part of the coagulum produced by a strong 

 solution of acetate of soda was afterwards freed from that salt 

 by i^ressure, it redissolved in pure water, and the solution was 

 again coagulated by a fresh addition of the salt. An experiment 

 with acetate of lime gave the same result. 



" The nitrates and chlorides coagulate also with great dif- 

 ficulty. 



" Solutions of sulphate of soda, magnesia, and lime coagulate 

 as readily as a liquid containing the same quantity of sulphuric 

 acid in the free state. On examining one of these mixtures, 

 the sulphuric acid was found in the solid part of the coagulum, 

 as before, and the alkali in the fluid part, united with the 



