374 STATE BOARD OF AGRICULTURE. 



LIME-SULFUR SPRAY. 



BY JAMES B, HARRIS. 



PART I 



METHODS OP ANAIA'SIS. 



The methods of analysis outlined in the following pages were devel- 

 oped preliminary' to the investigations upon the manufacture and stor- 

 age of the lime-sulfur spray reported in part II of this bulletin. The 

 methods that have been in most general use are those described by 

 Avery (1) and Haywood (2). These have been slightly modified from 

 time to time by other investigators, but at best they are tedious of opera- 

 tion and time consuming. 



Recognizing the need of improvement in the analytical methods, an 

 attempt was made to modify them with the idea of securing greater ac- 

 curacy and rapidity. The main differences between the methods herein 

 described and those in common use lie in the manner of effecting the 

 oxidation of the sulfur compounds and in the estimation of the mono- 

 sulfide and total sulfide sulfur, and the length of time required to make 

 a complete analysis of a sample of lime-sulfur solution is reduced from 

 more than one day to only a few hours. This in itself is an important 

 feature where a large number of analyses must be made. 



In all of our work 25 cc. of the concentrated solution was diluted to 

 250 cc. and the following determinations were made: 



(a) Total sulfur. 



(b) Mono-sulfide sulfur. 



(c) Thiosulfate sulfur. 



(d) Sulfite and sulfate sulfur. 



(e) Total sulfide sulfur. 



(f) Calcium oxide. 



A description of the methods follows: 



Total sulfur. — As it is a well known fact that sodium peroxide is a 

 very powerful oxidizing agent, it was substituted in our work for the 

 usual oxidizing agents bromine water and hydrogen peroxide, and was 

 found to give excellent results. The method of procedure is as follows : 

 10 cc. of the diluted solution is placed in a tall beaker, covered with a 

 watch glass and five or six grams of sodium peroxide added. After stand- 

 ing a few minutes, hydrochloric acid is added with stirring until the solu- 

 tion clears up. If all the sulfur has not been oxidized, this will be in- 

 dicated by a milky precipitate after the solution has been made acid. 

 The addition of a little more sodium peroxide will complete the oxida- 

 tion. In general however, five or six grams of sodium peroxide will be 

 sufficient. After boiling a few minutes to drive off the dissolved gases, 

 the sulfur may be precipitated as barium sulfate. This method of effect- 

 ing the oxidation is more convenient and rapid than either the bromine 



(1) Bulletin 90, page 104, Bureau of Chemistrj'. 



(2) " 101, 



