170 



Table of corrections for tlie temperature. 



Dry substance. 



Temperature of the 

 prisms in C. 



(h) By areometric methods, as found on pages 65-67, Bulletin 107. If time permits 

 it would be well to determine the per cent of water in a number of sugar solutions by 

 methods (g) and also (h) and (6). The comparison being between results of (g) and 

 (6) and (h) and (6). The results could be reported as special samples under (g), 

 giving kind of sirup, also figures obtained by (g), (6), and (h). 



(2) Polarimetric determinations. Effect of various clarifying agents on both samples. 



Weigh out a normal weight and make up to 100 cc, or to such a multiple thereof as 

 may be necessary to secure an accurate polarization, after clarifying as follows: 



(a) With lead subacetate solution. (Bull. 46, pp. 38-39; also Bull. 107, p. 40.) 

 Try at least two different quantities of the clarifying agents, reporting the separate 

 polarization. 



(6) With normal lead acetate solution. (Saturated solution of lead acetate in 

 water.) 



(c) With Home's dry lead subacetate. (J. Amer. Chem. Soc., 1904, 26 : 186.) 



(d) With Herles' solution. No. 1, 250 grams lead nitrate to 500 cc water; No. 2, 

 25 grams sodium hydroxid to 500 cc water. Use equal parts of each solution, 

 either 5 cc each or up to 10 cc of each. Note whether increased amount changes the 

 polarization. 



(e) W T ith alumina cream and hydrosulphite (sodium Ijydrosulphite, B. A. S. F. or 

 "Blankit"). This with the dry subacetate can be obtained from any of the large 

 dealers in chemical supplies. In this clarification make solution up to required 

 volume, then add a few crystals at a time until decolorization is effected. Polarize 

 at once after filtering and again after standing for some time. Should the solution 

 become cloudy on standing add some kaolin and shake, filter. Also try the following 

 method of procedure: In a solution after clarifying with alumina cream and filter- 

 ing, just before screwing on cap of polarization tube, add a few crystals of the hydro- 

 sulphite and shake. Polarize immediately ; note whether on standing there is a change 

 in the polarization. 



(J) Invert portions of a, 6, c, d, and e and determine the invert reading. Where 

 lead has been used take out the excess with some crystals of potassium oxalate or dry 

 sodium carbonate. Inversion can be accomplished by following (c), page 40, Bul- 

 letin 107, or (1), page 39, Bulletin 46, Revised. If the latter reference is used, the 

 equation should read: 



a-b 



S=- 



142.66- s: 



