366 REPORT OF THE CHEMIST OF THE 
The data in the preceding table suggest (1) that when the 
smallest amount of lime is used, the sediment consists more 
largely of uncombined sulphur; (2) that the amount of sulphite 
sulphur tends to increase with the amount of lime used; (3) 
that the amount of sulphate sulphur is usually insignificant. 
(4) Relative efficiency of different formulas.— By efficiency 
in this connection we mean the strength of a lime-sulphur 
wash in respect to the calcium pentasulphide (CaS,) present. 
This definition is based on the hypothesis that calcium penta- 
sulphide is the most effective compound in the golution for 
killing scale-insects. On this hypothesis therefore, it is desir- 
able to have in the lime-sulphur preparation the largest possi- 
ble amount of this compound. A _ consideration of the 
composition of the solution and sediment does not by itself 
serve fully to give us a complete idea of the relative efficiency 
of the different formulas used in preparing the lime-sulphur 
mixture. This can be definitely brought out only by ascertain- 
ing the amount of sulphur in different forms and of lime ap- 
pearing in the solution and sediment, as compared with the 
amount of the two constituents used. For example, we used in 
every case 125 pounds of sulphur; now, it is desirable to know 
what became of this amount,— how much went into solution in 
different forms and how much went into the sediment either as 
unchanged sulphur or in combination. It is instructive to fol- 
low in a Similar manner also the distribution of the lime in the 
solution and in the sediment or undissolved portion. Results 
are presented in the following table in such a way as to enable 
us to gain this information approximately. If our results 
were absolutely accurate, we should be able to show that the 
amount of lime and of sulphur in the dissolved and undis- 
solved portions are just equal to the amounts used; but owing 
to the difficulty of taking strictly accurate samples of the sus- 
pended materials and to imperfect methods of analysis, some 
discrepancies inevitably appear, though not sufficiently serious 
to impair the value of the results obtained. 
