312 EXPERIMENT STATION EECORD. [Vol. 36 



35, p. 207) with the view of determining the effect of storage; of lime added 

 after dilution ; of varying the lime-sulphur ratio, the period of boiling, and the 

 concentration; the occurrence and relation of calcium sulphite; the ratio of 

 jpolysulphid to thiosulphate ; the lower polysulphids and the effect of an ex- 

 cess of lime ; and the higher polysulphids and the effect of oxidation. 



The reactions, some of which are reversible, which determine the composition 

 of lime-sulphur solutions are rather numerous. The points of equilibrium vary 

 according as the solution is hot or cold, dilute or concentrated, or exposed to 

 the influence of other varying conditions. " Under such circumstances the only 

 way in which laboratory studies can be of practical value is by so thoroughly 

 establishing the fundamental principles involved and the effect of varying con- 

 ditions upon the relative importance of such principles as to aiford a sound 

 basis for reasoning." 



The general reactions between lime and sulphur on boiling with water are 

 indicated as follows: 



( 1 ) 3Ca ( OH ) 2+12S=2CaS6+CaS203+3H20 



(2) 10CaS5+3Ca(OH)2=12CaS4+CaS.Oo+3H20 



(3) CaS4-i-S=CaS= 



All lime-sulphur solutions are considered to be subject to hydrolytic decom- 

 position according to the following equation, the equilibrium being destroyed 

 by the reaction proceeding to the right with a rise of temperature : 



(4) CaS,+H20^Ca(OH)2+H2S+(x-l)S 



The products on the right side of the equation further react, giving, in the case 

 of CaSs, 



(5) CaSB+3H20=CaS203+3H2S 



"A well-boiled solution, not originally made with an excess of lime, can never 

 under any circumstances possess a plus reaction figure — that is, it can not con- 

 tain calcium hydroxid in excess of monosulphur. If originally made with an 

 excess of lime or if not boiled long enough, excess lime is at first present in solu- 

 tion. But if such a preparation be allowed to stand quietly and cool off in the 

 cooking vat, the indications are that the undissolved lime soon settles down, 

 while the small amount of dissolved lime rapidly reacts with polysulphur ac- 

 cording to equation 2, so that in this case, also, unless the cooled solution is 

 again stirred up with the .sediment, a plus reaction figure can never be present 

 in the end. But such a solution will naturally contain a notable amount of 

 tetrasulphid." 



It is indicated that with an increasing concentration the time of boiling 

 should also be increased. " With increasing concentration the utilization of 

 both lime and sulphur possibly becomes less nearly complete, and also the 

 polysulphids formed possibly contain a somewhat less proportion of pentasulphid. 

 But the apparent effect might have been produced simply by insufficient boiling, 

 and in any event it is of no material significance in comparison with the prac- 

 tical importance of putting out proprietary preparations in highly concentrated 

 form. 



" Finished solutions, if stored over sediment which contains free lime, will 

 naturally tend to maintain a plus reaction figure, and will undergo changes at- 

 tributable to the slow progress of reactions 1 and 2. If decanted from sediment 

 and preserved from access of air, only two slight changes are noticeable; first, 

 the progress of equation 5 until a certain concentration of hydrogen sulphid is 

 reached, when equilibrium is established according to equation 4; second, an 

 apparent slight drop in the thiosulphate figure, for which no explanation is of- 

 fered, since the phenomenon appeared too quantitatively insignificant to warrant 

 special investigation. Both changes, in fact, are so slight as to be entirely 

 negligible for practical purposes and under ordinary conditions." 



