EXPERIMENT STATION REPORTS. 



129 



TABLE NO. I. 



From the exporimeiits we found, as may be seen from the tablt^', 

 that the sohibilitv and the strength of the blue solution correspond 

 closely, although strictly speaking not all that dissolved was coloring 

 matter. At this point, it may be stated that the residue was chiefly 

 calcium carbonate and that the blue solution from the different sam- 

 ples varied in the amount of red pigment they contained. For example, 

 the solutions of azolitmin and the samples marked "litmus cubes," 

 "No. 1" and "No. 2" when slightly alkaline were very near to a true 

 blue, while the others were more or less of a blue violet. 



In making a standard solution from any sample of litmus, the num- 

 ber of grams required to make one hundred cubic centimeters of the 

 standard — ascertained by experiment- — is placed in a beaker, one hun- 

 dred cubic centimeters of distilled water added and placed in the 

 incubator over night or in flowing steam for thirty minutes. The in- 

 soluble residue is allowed to settle, then the solution is decanted on 

 a filter. The filtrate is the standard solution. However, if it is desired 

 to make a standard solution from a sample that has a large percentage 

 of insoluble material, it is best prepared by adding five hundred cubic 

 centimeters of water instead of one hundred and concentrating the 

 filtrate to one-fifth its volume over a water bath as the residue— if made 

 direct — will retain a large proportion of the solution. 

 17 



