Discussion of Results. 



It is evident that while both the sucrose and the lead subacetate 

 had a marked effect, that of the sugar was greater. By reducing the 

 amount of lead subacetate solution from 25 cc to 5 cc it was not 

 possible to attain on subtest 2 the empirical lead number 1.473 or 

 1.503 obtained on the straight maple sirup in tests A-l and B-l, 

 respectively, which numbers should have been very closely ap- 

 proached to permit the quantitative use of the Winton lead number. 



In the writer's modification, given on page 8, the solvent action 

 of the sugar appears to be satisfied in preventing the precipitation 

 of the lead sulphate, which would naturally precipitate on the addi- 

 tion of the lead subacetate solution subsequent to the addition of 

 the potassium sulphate solution. The maple lead compound is then 

 free to precipitate and under the conditions specified appears to give 

 proportional results. 



In the determination of the actual lead number on 25 grams of 

 the straight maple sirup the maximum number (1.503) was obtained 

 in series B, in which there was present in the filtrate 151.8 per cent 

 excess of lead. The corresponding lead number in series C was 1.399 

 with 102.4 per cent apparent excess of lead. In the latter case 

 0.7077 gram of lead was added and, using the weight (0.3757 gram) 

 precipitated in series B as the basis for calculation, there was present 

 88.4 per cent excess of lead, yet a decidedly low result was obtained. 

 It would therefore appear that to obtain the maximum precipitation 

 on straight sirups at least 150 per cent excess of lead should remain 

 in the filtrate. 



When 5 grams only of maple sirup were used, i. e., subtest 3, a 

 maximum precipitation was obtained in series D, in which an empi- 

 rical lead number 1.722 was obtained with 452.3 per cent excess of 

 lead. In E-3 a lead number 1.666 was obtained with 177.2 per cent 

 excess of lead, which was a slight drop from the previous test and 

 w,ould further indicate that at least 150 per cent excess of lead should 

 be present for maximum precipitation. 



On the mixed sirup in test D-2 the ratio of lead to sirup was 1:2.5 

 and an actual lead number 0.238 was obtained with 700.5 per cent 

 excess of lead. In E-2 the ratio was 1 : 5 and an actual lead number 

 0.240 was obtained with 284.2 per cent excess of lead. With a reduc- 

 tion of 416 per cent excess of lead the increase in the actual lead 

 number is scarcely perceptible, and, from the results obtained on the 

 straight sirup, it would not seem that a further reduction in the excess 

 of lead would give a further increase in the actual lead number on 

 mixed sirups. 



With respect to the desired excess of lead it appears that on all 

 sirups, both straight maple and mixed cane sugar and maple sirups, 



[Cir. 53] 



