10 



4. In effecting the polarization of substances containing sugar, half-shade instruments, 

 or triple field, only are to be employed. 



5. During the observation the apparatus must be in a fixed position and so far removed 

 from the source of light that the polarizing nicol is not warmed. 



6. Sources of light may be gas, triple burner with metallic cylinder, lens and reflector; 

 gas lamps with Auer (Welsbach) burner; electric lamp; petroleum duplex lamp; sodium 

 light. Several readings are to be made and the mean thereof taken, but any one reading 

 must not be neglected. 



7. In making a polarization, the whole normal weight for 100 cc is to be used, or a multiple 

 thereof for any corresponding volume. 



8. As clarifying and decolorizing reagents "there may be used: (a) Subacetate of lead (3 

 parts by weight of acetate of lead, 1 part by weight of oxid of lead, 10 parts by weight of 

 water); (6) alumina cream; (c) concentrated solution of alum. Boneblack and decolorizing 

 agents are to be excluded. 



9. After bringing the solution exactly to the mark, at the proper temperature, and after 

 wiping out the neck of the flask with filter paper, all of the well-shaken clarified sugar 

 solution is poured upon a dry rapidly acting filter. The first portions of the filtrate are to 

 be rejected and the rest, which must be perfectly clear, used for polarization. 



ERRATA. 



Page 27, under "1. Determination of water, (a) By drying, (3) 

 Provisional method for drying molasses with quartz sand," third line 

 from the end of section, for " (See method II (d) under 'ash')," read 

 " (See method (a) (5), page 31, under ' 2. Ash')." 



Page 30, three lines from bottom of page, for "50" read " 50 ". 



Page 39, formula under "(b) Optical methods by inversion, (1) 

 Method of Clerget," should read "100(a b)" in the numerator 

 instead of "a b." 



Page 40, fourth line from top of the page, under "Creydt's method 

 for determining rafnnose and sucrose together," transfer "at 20" to 

 the end of the sentence. 



IV. METHODS FOB THE ANALYSIS OF DAIRY PRODUCTS. 



Seventeenth. Convention, 1900, Bui. 62. 



Page 47, under " (2) Determination, (a) Soluble acids," insert in 

 the third line, after "saponified," the following: "or the saponification 

 may be conducted in a flask connected with a reflux condenser." 



Page 48, under " (h) Determination of saponification equivalent 

 (Koettstorfer number), (2) Determination," change the words "Be- 

 tween 1 and 2 grams" to "Approximately 2.5 grams". At the end of 

 the same sentence, insert the following after a semicolon: "or the 

 saponification may be conducted in a flask with a reflux condenser". 



Page 50, make such changes in the quantities of sodium thiosulphate 

 as will be consistent with the new atomic weights. 



