90 JOURNAL OF THE , 



of the eocene surface rock, while at or near tide level, was followed 

 by a submergence, at which time the post pliocene deposits along- 

 near the shore were made ; following this was a re-elevation to a 

 point higher than that of present time by probably at least six ta 

 seven feet, and now, as pointed out above, the re-subsidence ap- 

 pears to be in progress. 



SOLUBILITY OF BARIUM CHROMATE. 



J. F. WILKES. 



The proposition has frequently been made to determine barium 

 as chrt)mate, and to separate barium from stroutium and calcium, by 

 means of potassium bichromate. Meschezerski (Zeit. Anal. Chem., 

 21, 399) enumerates several objections to the method, as the difficultly 

 soluble nature of stroutium chromate, the solubility of barium 

 chromate, and its tendency to carry down foreign salts with it. 



A few experiments were undertaken to further test this matter. 

 Solutions were prepared, one of BaClg, (1 c c. = .0222 Ba), SrCl^ 

 (saturated), KoCroO^, (1 c. c. =.03167, K^Cr^O,, and 1 c. c.=.3I67). 

 The barium solution and chromate solution were mixed in varying 

 proportions in a flask which was corked and shaken three or four 

 times a day for about four days. The flasks stood in a room of 

 fairly equable temperature, (about 15^C). The contents were then 

 filtered, 50 c. c. taken, and both barium and chromium sesquioxide 

 determined in duplicate. These experiments related simply to the 

 solubility of barium chromate and stroutium chromate. No mix- 

 ture of the two was made nor attempt at separating them. 



In three experiments it was found that where 4.50 grams of potas- 

 sium bichromate were present per litre, .434 grams of barium chro- 

 mate were held in solution; with 11.06 grams KgCr-^O^, there were 

 .278 grams BaCr04; with 20.10 grams KoCrj^O,, there were .192 

 grams BaCrO^. This would go to prove that the stronger the solu- 

 tion of potassium chromate used, the more complete is the precipi- 

 tation of barium. 



To obviate the difficulty about the insolubility of stroutium chro- 

 mate, some have recommended the addition of a little acetic acid as 

 dissolving the stroutium without affecting the solubility of the 

 barium. By the addition of less than one per cent, of acetic acid, 



