Cubic Grams. centimeters. Grams. Grams. Grams. Grams. 0.1000 54 0.1851 0.0008— 0.0004— 0.0003— 0.1000 58 0.1854 0.0005— 0.0002— 0.0002— 0.1000 51 0.1859 0.0000 0.0000 0.0000 0.1000 50 0.1854 0.0005— 0.0002— 0.0002— 0.1000 48 0.1859 0.0000 0.0000 0.0000 0.1000 52 0.1854 0.0005— 0.0002— 0.0002— Considerable difficulty, however, was experienced in obtaining satisfactory determinations of potassium associated with sulfuric and phosphoric acids. As Caspari has pointed out, the sulfuric acid must be removed by precipitation as barium sulfate before the treatment with perchloric acid is attempted, and unless the precipitation is made in a strongly acid solution, some potassium is carried down with the barium. Phosphoric acid need not be previously removed, but to secure a nearly complete separation of this acid from the potassium, a considerable excess of perchloric acid should be left upon the potassium perchlorate before it is treated with the alcohol. When these conditions are carefully complied with, fairly good results may justly be expected. Below is given a number of the results obtained: (A) = Volume of filtrate. Cubic centimeters. (B) = Potassium perchlorate found. (C) = Error on potassium perchlorate. (D) = Error on potassium chlorid. (E) = Error on potassium potash. Compounds taken. (A) (B) (C) (D) (E) Grams. Grams. Grams. Grams. Grams. Potassium chlorid = 0.10 Calcium carbonate = 0.13 50 0.1887 0.0027+ 0.0014+ 0.0005+[231] Magnesium sulfate = 0.13 82 0.1875 0.0016+ 0.0008+ 0.0005+[232] Ferric chlorid = 0.05 80 0.1861 0.0002+ 0.0001+ 0.0001+[233] Magnesium sulfate = 0.05 80 0.1843 0.0016- 0.0008- 0.0005-[234] Manganese dioxid = 0.05 92 0.1839 0.0020- 0.0010- 0.0006-[235] Sodium phosphate = 0.40 60 0.1854 0.0005- 0.0002- 0.0002-[236] In the last three experiments of the above table the amount of perchloric acid was about three times that required to unite with the bases present, and the phosphoric acid subsequently found with the potassium was hardly enough to appreciably affect the weight, although its absolute removal was found impossible.