[snell] analysis of MAPLE PRODUCTS 169 



this very convenient bridge and telephone there was no difficulty in 

 obtaining a sharp minimum of sound. The conductivity cell used 

 at first was of the form represented in Fig. 295 (p. 402) of Ostwald & 

 Luther's 'Thysiko-Chemicher Messungen," 2nd edition (1902). Its 

 capacity was about 50 c.c. It had electrodes of 2 «5 cm. diameter 

 set 1 cm. apart, which maintained their position satisfactorily, as was 

 demonstrated by repeated determinations of the cell constant. Later, 

 a special cell of the same type with extra heavy electrodes and with a 

 thermometer set in the cover was made for me by Messrs. Eimer and 

 Amend of New York. The platinum electrodes of this special cell 

 are of B. & S. gauge No. 27, and are 3-2 cm. in diameter. They are 

 adjustable as to distance, but are firmly held in position by set-screws. 

 The thermometer range is 20° to 30°, graduated in tenths. This type 

 of cell has proved perfectly satisfactory for the purpose. 



In routine work it might be advisable to have a considerable 

 number of cells fitting the same pair of electrodes. These could be 

 filled with the different samples and set in a thermostat to come to the 

 required temperature, when measurements of all could be made in rapid 

 succession. I have not used a thermostat in this work, but have regu- 

 lated the temperature by placing the conductivity cell in a beaker of 

 water of a suitable temperature, a fraction of a degree above or 

 below that desired, and stirring the contents of the cell with the 

 electrodes until the thermometer within the cell showed the correct 

 reading. 



The cell constant was determined by use of 0-1, 0-02 and O-OIM 

 potassium chloride solutions, made up at 18° C. from the ignited C.P. 

 salt, assuming for these at 25°C. the conductivities 1289, 276-8 and 

 141-2 X 10-5*. 



Range of Variation of the Conductivity Value in Genuine Syrups. 



In addition to the 43 syrups referred to above, the conductivity 

 value has been determined on 22 syrups made in this laboratory in the 

 season of 1912. See table III. These syrups were all made from the 

 sap of ten trees — six hard and four soft maples. They represent the 

 runs of different days from April 6th to April 29th, and some were made 

 from the sap of the soft maples alone, others from the hard maples only, 

 though the majority represent the mixed sap of the ten trees. They 

 were boiled down in basins on gas stoves with the exception of one 

 (No. 5) which was evaporated on the steam bath. These 22 syrups 

 show a range of 119 to 164, average 143. This is a total range of 31-4%. 

 This is about the same range of variation as is shown by the total ash, 



* Ostwald-Luther, Physiko-cheniischer Messungen, 2nd edition, p. 407. 

 Sec. Ill, 1913—11 



