166 THE ROYAL SOCIETY OF CANADA 



The most rapid methods hitherto proposed have depended upon 

 precipitation with lead subacetate and measurement of the volume 

 of the centrifugally-settled precipitate.* No great delicacy has been 

 claimed for these methods, and even they require more time than a 

 conductivity measurement. 



The Conductivities of Undiluted Pure Syrups. 



Measurements of the conductivities of the undiluted syrup have 

 been made upon 43 samples, all of Canadian origin. Eleven pairs of 

 early and late products from the same or adjoining woods were sent 

 me by the makers from various parts of the Province of Quebec in the 

 season of 1911. Thirteen samples from Ontario and six from Quebec, 

 all of the season of 1911, were kindly forwarded to me by Dr. Anthony 

 McGill, Chief Analyst of the Inland Revenue Department, Ottawa, 

 as fairly representative of the 450-odd samples collected by the Depart- 

 ment for the purpose of establishing a standard of purity for maple 

 syrup. Each of these was accompanied by a declaration of genuineness 

 signed by the maker, f The remaining two samples of the 43 were 

 made from identical sap, one by rapid boiling in a modern evaporator 

 having a corrugated pan, the other in an iron kettle, not entirely free 

 from rust, with very slow boiling. 



A summary of the variations of the specific gravity and of the 

 electrical conductivity of 42 of these 43 syrups is given in Table I. The 

 syrup omitted from this summary is one of the Inland Revenue Depart- 

 ment samples, which was of extremely low density. Its specific gravity 

 was 1*279, its moisture content (according to the analysis made in the 

 Inland Revenue Laboratory) 38-59%, and its conductivity (x x 10^) 45 • 0. 



As a general rule, the syrups of high density showed low conduc- 

 tivities and those of low density showed high conductivities. This 

 indicates that in undiluted syrups the concentration of the sugar has 

 more influence upon the conductivity than has the concentration of 

 the electrolyte components. 



Zuckerind., 60, p. 359, Chem, Abstr. 4, p. 1554 (1910) have proposed methods of estim- 

 ating the ash of sugars and syrups from their electrical conductivities. These methods 

 appear to have given.good results in the hands of their authors but have been ad- 

 versely criticised by others — Reichert's by Fock and Plath, Zeit. Ver. Zuckerind., 

 39, p. 710 (1889), Main's and Lange's by A. Trenkler, Oesterr-ung. Zeit. Zuckerind., 

 39, p. 437, Chem. Abstr., 4, p. 308 (1910). 



* Hortvet, Journal American Chemical Society, 26, p. 1543 (1904) Bureau of 

 Chem. U.S. Dept. Agr., Bulletin 107, p. 72; Jones, Vermont Agr. Expt. Station, 

 18th Annual Report, p. 322 (1904-5). 



t See Bulletin 228 of the Laboratory of the Inland Revenue Department. (1911). 

 The syrups examined were Nos. 184-191, 193-195, 211-214, 263, 278, 281 and 284 

 of that Bulletin. 



