Chemical Papers. 57 



As previously stated, it has been assumed from the absence of 

 appreciable quantities of sulfite and sulfate that the balance of the 

 calcium is combined as sulfides. This fi*gure obtained by sub- 

 tracting oalciuta in the thiosulfate from the total calcium as given 

 in the third column of table I. 



In the third column, the sulfur calculated from the percentage of 

 calcium thiosulfate is given, and in the fourth column the difference 

 between this last and the total sulfur is given as sulfur in sulfides. 



The percentage of calcium and sulfur in calcium thiosulfate to 

 the total calcium and sulfur is given in the fifth column. 



The days in the first column of each table, of course, cor- 

 respond. 



There is much difference of opinion among authorities concern- 

 ing the sulfides of calcium. Contradictory statements may be 

 found regarding even the more common sulfide, the monosulfide, 

 and opinions differ as to whether or not the others have ever been 

 prepared in a pure state. According to Mendeleeff,* in an ad- 

 mixture with calcium thiosulfate, by boiling a solution of lime or 

 calcium monosulfide with sulfur, calcium pentasulfide is formed, 

 according to this reaction : 



3Ca(OH)2 + 12S = 2CaS5 ^ CaSaOs + 3H2O. 



The same authority ignores the existence of any polysulfides be- 

 tween the mono- and the pentasulfide. 



According to Dammer,f both the penta- and the tetrasulfide 

 exist, and may be prepared by boiling calcium monosulfide with 

 the proper proportion of sulfur and water. He recognizes two 

 other compounds also — Herschell's crystals, having the formula, 

 3CaO.CaS4.12H20, and Bushner's crystals, 4CaO.CaS.18H20, 

 which may be formed under slightly modified conditions. 



To quote Watts :!{: "When CaS is boiled with S and H2O it dis- 

 solves, forming an orange-red solution, the quantity of S which 

 goes into solution corresponds with that required to form CaS4 and 

 CaSs ; if more S is used, it is deposited on cooling the liquid ; if 

 less S than S3 to CaS is used, some of the CaS remains undissolved. 

 Both solutions are decomposed on concentration with precipitation 

 of Ca(0H)2 and S and evolution of H2S," 



It is seen that there are several possible compounds of calcium 

 and sulphur which might be present in the dip. No attempts 

 were made to separate the sulfides other than the single unsuccess- 

 ful attempt by freezing, and consequently the data given in this 



* Mendeleeff 's Principles of Chemistry, vol. II, p. 214. 



t Dr. O. Dammer, Handbuch der Anorganischen Chemie, II Band Theil, p. 311. 



t Watts's Dictionary of Chemistry, vol, I, p, 214. 



