[snell] analysis of MAPLE PRODUCTS 167 



The syrup made in the h-on kettle had a specific gravity of 1 -326, 

 and a conductivity of 25*9, while that made from the same sap by rapid, 

 shallow boiling in an evaporator showed a specific gravity of 1'334, 

 and a conductivity of 22 '4. This is in harmony with the general 

 rule of lower conductivity accompanying greater density. The minimum 

 conductivity (9 «6) was shown by the syrup of maximum density 

 (1'355), while the maximum conductivity (33 -6) was found in a syrup 

 of density 1'311. 



The Effect of Dilution. 



The results of the above measurements indicate that as the water- 

 content of maple syrup increases the conductivity increases. In other 

 words, the more dilute the solution the greater the conductivity. This 

 is not in line with the usual behaviour of aqueous solutions of electrolytes. 

 In general, the specific conductivity of such solutions decreases with 

 dilution. The thought, therefore, suggested itself, that if one continued 

 to dilute maple syrup with water a point of dilution must eventually 

 be reached at which the conductivity would cease to increase and begin 

 to decrease — a point of maximum conductivity. This proved to be 

 the case, the maximum occurring at a dilution of one volume of syrup 

 to two of water, i.e., in a mixture containing 33^ per cent., of syrup by 

 volume, or 39-6% of syrup of normal density (1-320) by weight. 



Table II and Diagrams I and II give results typical of the effect 

 of dilution upon the specific conductivities of maple syrups. 



On each side of the point of maximum conductivity there is a 

 considerable range of concentrations, within which the conductivity 

 differs very little from the maximum. This renders it possible to measure 

 the maximum conductivity of diluted maple syrup without observing 

 much precision in making up the mixture of maple syrup and water. 

 This is a point of great practical advantage in relation to the rapidity 

 of the method. It is not necessary to weigh the syrup nor to reduce 

 it to a definite density. An ordinary 25 cc. graduate can be used to 

 measure the syrup, the two portions of water subsequently measured 

 from the same graduate serving to rinse out the syrup which adheres 

 to the sides. 



The range of variation of the conductivity of pure maple syrups 

 thus diluted with two volumes of water is much narrower than that 

 of the conductivity of the undiluted syrups. The mean conductivity 

 at 25° C. {X X 10^) of the diluted solutions of the 42 syrups of Table I 

 was 153 — over 8 times the mean conductivity of the same syrups in 

 the undiluted state. The minimum was 120, the maximum 203 — the 

 latter being the conductivity value of the syrup made in the iron kettle. 

 The minimum deviates from the mean by 21 per cent., as against 49 



