l)ixoN AND Mason — Crijoscopic 3Iethod for Eistimation of Sucrose. 3 



Table I. 



It will be observed tbat a thermo-couple as sensitive as that used in this 

 calibration can only register depressions of freezing-point up to 0-849° 

 (294,-5 iirni. = V). This limitation, of course, is imposed by the scale. 

 Where the solution to be examined has a greater depression than this, it is 

 necessary to substitute for distilled water a standard freezing below 0°. 

 Solutions of calcium chloride, whose depressions have been previously deter- 

 mined, can be employed. Though this solution may be used in place of 

 distilled water in these cases, it is not as easy of manipulation as a pure 

 liquid, where ice may continue to separate without alteration in freezing- 

 point. On the whole, it has been found more satisfactory, where a greater 

 range is desired, to construct a less sensitive thermo-couple, and to keep 

 distilled water as the standard. 



Estimation of Sucrose in made-u}) Sohdions. 



To effect the inversion of sucrose, small quantities of iuvertase prepared 

 by Davis' method (1) were used. It is undesirable to dilute unnecessarily 

 the solution, so only that quantity of invertase is added which will ensure 

 inversion. Allowance must subsequently be made for the dilution of the 

 solution with the water added in the invertase, and also for the depression 

 of freezing-point produced by the solutes in the invertase solution and 

 the toluene added with it. The invertase solution employed had a moisture- 

 content of 83 per cent. 



In each of the observations two test tubes of about 10 c.c. capacity were 

 used. Into one approximately 5 gm. of the sucrose solution (2gm. of sucrose 



b2 



