was made to contain 65 per cent of cane sugar. Mixtures were made 

 of C one part, 8 one part; C one part, 8 three parts; D one part, 

 S one part ; D one part, S three parts, all by weight. The lead num- 

 bers were then determined on the sirups C and D and on the mixtures 

 in the usual manner, with the following results: 



, 



Winton lead numbers on known mixtures (Hendrickson). 



ERROR INTRODUCED BY CARBON DIOXID IN DISTILLED WATER. 



Winton a determines the standard of the lead subacetate solution 

 in 25 cc by the lead sulphate method in the same way as in the test 

 itself. On diluting 25 cc of the lead subacetate solution to 100 cc, 

 precipitation of the lead occurs which varies from an opalescence to 

 a decided turbidity, depending upon the quality of the distilled water. 

 The distilled water used in the following experiments was either freshly 

 boiled and the containing vessel connected with a soda lime tube 

 while cooling, or redistilled from caustic potash. The water pre- 

 pared by either method gave an opalescence or slight turbidity in 

 the blank test, which turbidity appeared within five minutes after 

 making the dilution but did not materially increase on standing in a 

 stoppered flask for three hours. This time was adopted as the mini- 

 mum, since one hour failed to give uniform results. To ascertain the 

 amount of lead precipitated in the blank or standard, determinations 

 were made upon 10 cc aliquots before and after filtering, with the 

 following results: 



Weight of lead sulphate from 10 cc 



Unfiltered... 



Filtered. . 



Gram. 



0. 1673 

 .1676 

 .1645 

 .1645 



This difference is not so important on pure maple sirups, but on 

 mixtures, especially those containing small percentages of maple, the 

 error arising in the determination of the lead number is very marked 



. Amer. Chem. Soc., 1906, 28: 1205. 



[Cir. 53] 



