AGRICULTURAL CHEMISTRY — AGROTECHNY. 611 



The mean densities and conductivities of 42 genuine maple sirups were found 

 to be 1.333 at 15° C. and 18.7 {K X 10°) at 25°, the minimum 1.805 and 9.6, 

 and the maximum 1.355 and 33.6, respectively. A sirup not included in the 

 42 samples showed a specific gravity of 1.279, a conductivity {K X 10°) of 

 45, and a moisture content of 38.59 per cent. As a general rule, sirups of high 

 density show low conductivities and sirups of low density high conductivities, 

 indicating that in undiluted sirups the concentration of the sugar has more 

 influence upon the conductivity than has the concentration of the electrolyte 

 components. The measurements show that the more dilute the sirup the 

 greater the conductivity. When sirup is diluted with water to contain only 

 33J per cent of actual sirup by volume, a point of maximum conductivity 

 is reached. If the dilution is continued beyond this point the conductivity 

 begins to decrease. 



As on either point of maximum conductivity there is a considerable range 

 of concentration without which the conductivity differs very little, it is possible 

 to measure the maximum conductivity of a maple sirup without observing much 

 precaution in making uji the sirup-water mixture. "The mean conductivity at 

 25° (K X 10°) of the diluted solutions of the 42 sirups [mentioned above] was 

 153, or over eight times the mean conductivity of the same sirups in the un- 

 diluted state. The minimum was 120, the maximum 203. the latter being 

 the conductivity value of the sirup made in the iron kettle. . . . Genuine 

 sirups have given values of 110 to 200. but further experience may extend 

 these limits a little. Sirups giving conductivity values distinctly outside these 

 limits may be condemned. Those giving normal values are not necessarily 

 pure and should be further examined by well-established tests." 



In addition to the 43 sirups mentioned above, 22 taken from the trees of 

 Macdonald College grounds and prepared in the laboratory were examined. 

 These showed a range from 119 to 164, with an average of 143. Three Vermont 

 sirups gave conductivity values of 110, 115, and 122. The minimum value 

 found in the work was 110 and the maximum 203. The highest value for a 

 sirup actually prepared for the market was 197. By weighting the 22 sirups 

 made from the trees on the Macdonald College farm as 2, a mean conductivity 

 value is obtained of 150. This is approximately equal to the electrical con- 

 ductivity of an 0.01 molar aqueous solution of potassium ehlorid (141.2)." 



No conclusions were drawn fi-om the results obtained as to the value of 

 determining the conductivity of the ash solution. 



The analysis of maple products. — II, A comparative study of the delicacy 

 of methods, J. F. Snell and J. M. Scott {Jour. Indus. an4 Engin. Chem., 5 

 {1913), No. 12, pp. 998-997). — In studying the value of the electrical conductivity 

 test for detecting adulterations in maple sirup it appeared desirable to compare 

 the delicacy of this test with that of other methods in vogue. Three sirups 

 were chosen for the experiment — one a light-colored sirup, another a mixture 

 of several pure sirups, and the third a sirup prepared at the Macdonald 

 College. 



The determinations made were insoluble ash and alkalinity of insoluble and 

 soluble ash (E. S. R., 17, p. 1038; 24, p. 266; 26, p. 661) ; soluble ash by differ- 

 ence ; conductivity value, by the method outlined in the preceding abstract ; 

 Canadian lead number; Winton lead number (E. S. R., 18, p. 420) ; Ross's modi- 

 fied Winton number (E. S. R., 22, p. 709) ; and Sy lead value (E. S. R., 20, 

 p.. 1106). 



In the work the rates at which the conductivity value, ash data, and the 

 various lead values fall off v,'hen maple sirup is diluted were noted. The 

 Canadian lead value showed the most rapid falling off, while the conductivity 

 value showed the narrowest range. The duplicates obtained by the Winton 



