MANUAL FOR SUGAR GROWERS. 87 



years ago, devised a method of testing based on the 

 use of litmus-paper as an indicator of the point of 

 neutrality. It is found, however, — and Dr. Shier's 

 directions for using his test contain a tacit admis- 

 sion of this fact, — that litmus-paper does not afford 

 a correct indication of the point of neutrality in cane- 

 juice ; hence the test had to be supplemented by 

 observations of the manner in which the flocculent 

 precipitate of the juice separated. This complicates 

 the working of the test and greatly impairs its use- 

 fulness. That litmus is not an accurate indicator in 

 the case of organic acids is perfectly well known, 

 and certain other bodies are now largely used in the 

 laboratory in place of it. 



" These considerations led the writer to make a 

 series of experiments with other indicators, when 

 it was found that phenol-phthalein could be em- 

 ployed with ease and certainty, and that it could be 

 placed in the hands of the workmen in charge of 

 the clarifiers, who quickly acquire the small degree 

 of skill necessary for its successful use. 



" The following are required for making the test : 

 test-tubes, a pipette, and a drop -bottle containing 

 a solution of phenol-phthalein in spirit ; and the 

 method of testing is as follows : 



" The clarifier is filled with juice, and lime added in 

 the usual manner. When the greater portion of the 

 lime required has been added, a little of the juice is 

 taken from the clarifier by sucking it into the pipette 

 with the mouth ; two of the test-tubes are about half 

 filled with juice from the pipette, and one or two 

 drops of the phenol-phthalein solution are added to 



