58 Kansas Academy of Science. 



paper throw little light on the manner in which calcium and sul- 

 fur are combined as sulfides. 



In the course of the investigation, of which this paper records 

 but a part, many dips were analyzed. Every dip, when analyzed, 

 gave percentages of calcium and sulfur combined as sulfides and as 

 calcium thiosulfate. These figures varied somewhat, but could al- 

 ways be assigned to a solution of various mixtures of monosulfide 

 of calcium, one or more of the polysulfides of calcium, and thiosul- 

 fate of calcium. 



For the sake of simplicity and for comparison, it is assumed that 

 the dip is a solution of a mixture of monosulfide of calcium, pen- 

 tasulfide of calcium, and calcium thiosulfate, the relative propor- 

 tions of which may vary, and of course would vary in a dip ex- 

 posed to the air, if they decompose at different rates. Some 

 illustrations may be given: 



2CaS.18CaS5.5CaS203. 

 5CaS.6CaS5.3<CaS203. 



It is not believed that so simple a mixture is the true one, but 

 for comparing results in the vat experiment the above possibility 

 is given. 



Some interesting facts may be noted by turning to table I. In 

 the first vertical column it will be seen that the specific gravity is 

 constantly and regularly increased. This increase is due, first, ob- 

 viously to concentration from evaporation of the water ; secondly, 

 to the oxidation of the sulfides. In the next column it will be seen 

 that the percentage of the calcium thiosulfate constantly increases, 

 the greatest increase occurring in the first three days of the experi- 

 ment. The total increase was 0.99 per cent, in the sixteen days, 

 an average of 0.063 per cent, per day. This increase in calcium 

 thiosulfate may be ascribed to two causes : First, to the concentra- 

 tion, as shown in the increase of specific gravity ; and second, to 

 the oxidation of polysulfides from the oxygen in the air : 



CaS5 + O = CaSaOs -f S3. 



( The rate of evaporation was found in a later experiment for the 

 same vat and same kind of dip to be 40.16 per cent, for sixteen 

 days ; so the thiosulfate from this cause alone would have increased 

 from 0.3 per cent, on the first day to about 0.5 per cent, on the 

 sixteenth day.) 



In the third column the percentage of total calcium shows a con- 

 stant and regular increase. There are at least two independent 

 agents acting here: First, concentration acting to increase the per- 



