2 BULLETIN 451, U. S. DEPARTMENT OF AGRICULTURE. 



parison of results. The lime used was prepared from chemically 

 pure calcium oxid by slaking and drying out, then passing through 

 an 80-mesh sieve. Its content in available calcium oxid was deter- 

 mined by the phenol solution method of Lindet and Brasart. 3 The 

 sulphur used was sifted U. S. P. flowers, assumed without analysis 

 to be sufficiently pure for the purpose. 



The methods of analysis have been fully described in the previous 

 papers referred to. For the sulphid-acid figure " Method B " was 

 employed, while the sulphid-base figure was not directly determined, 

 since it can be obtained with greater accuracy by algebraic addition 

 of the sulphid-acid figure and the reaction figure. All determina- 

 tions were performed in duplicate. 



EFFECT OF STORAGE. 



EXPERIMENT 1. 



The first series of experiments, as it happened, was directed toward a study 

 of the stability of lime-sulphur solutions during storage. A number of prepara- 

 tions made for another purpose had been partially analyzed when other matters 

 interrupted. On resumption of the work it seemed best to repeat all the de- 

 terminations previously executed. The results are given in Table 1, under 

 Experiment 1. 



The formulas employed were based on 100 parts of sulphur in all cases, while 

 the lime is expressed in proportional parts available calcium oxid. The pro- 

 portional parts of water given include both water added as such and the water 

 of hydration of the lime. The lime and sulphur were thoroughly mixed dry 

 in the container in which the solution was to be prepared — a 500 c. c. Kjeldahl 

 flask. The desired amount of water, usually 200 c. c, was then added gradu- 

 ally with thorough mixing. The mixtures were brought to boiling under reflux 

 in about five minutes, and only the period of actual boiling was counted. 

 Shortly before the end of the boiling period, during which the flask was fre- 

 quently shaken, a stream of illuminating gas washed through caustic-soda solu- 

 tion was introduced through a narrow tube passing down the condenser into 

 the neck of the flask. The flask was partially cooled under these conditions by 

 immersion in water, then the well-mixed contents were transferred to 4-ounce 

 " sample oil " bottles, which were filled into the necks and sealed. When cold 

 the bottles were thoroughly shaken to insure a uniform solution. 



The results of Experiment 1 show that within the range of prac- 

 tice, no matter what the formula or conditions of preparation may 

 have been, all lime-sulphur solutions stored after decantation from 

 sediment will acquire a distinct negative reaction figure in course of 

 time. Divers and Shimidzu 4 qualitatively showed the reversibility 

 of the reaction, simply stated: CaS x +2H 2 0<=*Ca(OH) 2 +H 2 S-f- 

 (x — 1)S. In Experiment 1 we evidently have quantitative data 

 relative thereto. The course of the equation from left to right is a 

 matter of hydrolysis and the reaction evidently will progress thus 

 in all solutions until inhibited by the accumulation of hydrogen sul- 

 phid, provided the latter is not allowed to escape. The more dilute 



