214 Oooch <ni<l Boynton — Estimation of Barium 



but the addition of a drop of water is sufficient to induce 

 immediate precipitation in the form of the hydrous salt. 



Incidentally it is interesting to note that when water acts 

 upon the colorless mixture of acetone and acetyl chloride the 

 solution becomes yellow, and then reddish, and develops a 

 distinctly fruity odor, condensation taking place between the 

 acetone and acetyl chloride. The boiling points of the col- 

 lected filtrates from a series of barium chloride precipitations 

 after standing about a week ranged from 50*5° to 250°, and 

 left a resinous residue at that temperature. 



From the results of the experiments described, it may be 

 inferred that the best conditions for the quantitative precipita- 

 tion of barium chloride by the acetone-acetyl chloride mixture 

 should be found in the use of minimum amounts of water, the 

 preservation of ordinarily low temperature, a liberal propor- 

 tion of acetone, and not too prolonged digestion of the precipi- 

 tate in the excess of the precipitant. These conditions have 

 been complied with in the quantitative tests. 



Barium chloride was prepared for the work by precipitating 

 it with strong hydrochloric acid from a water solution of the 

 presumably pure salt, recrystallizing twice from water, and 

 drying in the air. On gentle ignition the salt lost water cor- 

 responding to the ideal composition of the hydrous chloride, 

 BaCl 2 .2H 2 0. In each test a portion of this salt was weighed 

 out into a small beaker and dissolved in l cm3 of water. The 

 beaker was cooled by immersion in a water-bath preferably 

 supplied with running water at a temperature of about 15°. 

 To the cooled solution, constantly shaken, the acetone-acetyl 

 chloride mixture was added from a dropping funnel at the 

 rate of five drops to the second. Other data of the experi- 

 ments with barium chloride are given in Table I. The pre- 

 cipitate was filtered off upon asbestos in a perforated crucible, 

 dried, or ignited, and weighed as the anhydrous chloride, BaCl 2 . 

 From these results it appears that the best of the conditions 

 studied for the handling of 0*1 grm. of hydrous barium chlo- 

 ride are the solution of the salt in l cm3 of water, treatment 

 with 30 cmS of the 4: 1 mixture of acetone and acetyl chloride, 

 washing with acetone, and drying in the air-bath at 135° or 

 at low redness. 



The application of these conditions to the separation of 

 barium from moderate amounts of calcium and magnesium 

 proves to be easily feasible. When acetone is added to the 

 concentrated solution of calcium chloride or magnesium chlo- 

 ride in water two liquid layers are formed, the acetone above 

 and the aqueous layer below; but the addition of a few drops 

 of acetyl chloride renders the liquids miscible while further 

 addition causes no precipitation. When the 4:1 mixture of 



