378 



STATE BOARD OF AGRICULTURE. 



cium hydroxide present in the lime sulfur solution, so that the calcium is 

 present as the sulfide and thiosulfate together with a little as the sulfate 

 and sulfite. According to the reaction: CaSx-fl^^Calo+Sx, the 

 amount of calcium oxide in solution as the sulfide is given by multiply- 

 ing the number of cc. of N/10 iodine used in the monosulfide sulfur 

 determination by 0.0028. According to the reaction 2CaSo03-rl2f= 

 CaS^Oe+Calo, the amount of calcium oxide present in the form of the 

 thiosulfate is determined by multiplying the number of cc. of decinor- 

 mal iodine used in the thiosulfate determination by 0.0056. If there 

 is any sulfate or sulfite sulfur present the corresponding amount of 

 calcium oxide may be computed and added to the above. This method 

 of estimating the amount of calcium oxide by computation was com- 

 pared with the usual method in a series of fifteen experiments, and the 

 results are given in the Table III : 



TABLE III. 



No. of sample. 



cc. N-10 iodine 

 used in mono- 

 sulfide sulfur 

 determination. 



cc. N-10 iodine 



used in the 



thiosulfate 



sulfur 



determination. 



Sulfate 

 sulfite 

 sulfur. 



CaOby 

 computa- 

 tion. 



CaO Ex- 

 perimental 

 value. 



Difference. 



1. 



2. 

 3. 

 4. 

 5. 

 6. 

 7. 

 8. 

 9. 

 10 

 11 

 12 

 13 

 14 

 IS 



13.5 



17.15 



18.2 



18.05 



20.15 



15.50 



15.80 



25.20 



13.20 



26.3 



23.4 



20.4 



21.55 



13.65 



47.1 



4.25 

 5.65 

 5.35 

 5.25 

 5.95 

 4.30 

 6.35 

 7.70 

 4.. 50 

 5.55 

 6.25 

 5.70 

 6.75 

 4.20 

 3.75 



.03 

 none 

 none 



.05 



V 



.13 

 .03 

 .09 

 .05 

 .10 

 .03 

 .03 

 .08 

 .08 

 .02 

 .06 



6.20 

 7.97 

 8.09 

 8.06 

 9.15 

 6.79 

 8.22 



11.52 

 6.36 



10.52 



10.09 

 9.01 

 9.92 

 6.20 



15.37 



6.22 



7.97- 



8.22 



8.12 



9.14 



6.90 



8.12 



11.62 

 6.39 



10.61 



10.06 

 9.03 



10.00 

 6.30 



15.43 



.02 

 .00 

 .13 

 .06 

 .01 

 .11 

 .10 

 .10 

 .03 

 .09 

 .03 

 .02 

 .08 

 .10 

 .00 



These results indicate that the method of weighing the free sulfur gives more 

 nearly the correct result and in our later work this method has been used when- 

 ever a direct determination of the sulfide sulfur was desired. 



