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These slabs are composed of crystals of uniform size and of a pale green tint. But the geodes show some striking combinations of both crystals and colors with an exterior formed like box work, composed of a very heavy dark material said to be a mixture of barium, calcium and iron.
Of sodium and potassium hydroxide, it may be said that they can be used with all indicators, and their solutions may be boiled, but they absorb carbon dioxide readily and attack the glass of bottles, thereby losing strength; sodium carbonate may be weighed directly if its purity is assured, but the presence of carbonic acid from the carbonate is a disadvantage with many indicators; barium hydroxide solutions may be prepared which are entirely free from carbon dioxide, and such solutions immediately show by precipitation any contamination from absorption, but the hydroxide is not freely soluble in water; ammonia does not absorb carbon dioxide as readily as the caustic alkalies, but its solutions cannot be boiled nor can they be used with all indicators.
Their instruments are practically identical, consisting of a hollow cylinder a few inches long, one end of which is applied to the eye, the other end, instead of having a lens, being covered by a piece of paper smeared with a phosphorescent salt, the double cyanide of platinum and barium. It has not yet, I believe, been applied to thicker parts of the body.
On adding this chloride of barium to sulphate of copper solution, we get then a change which we might represent thus: Copper sulphate, consisting of a combination of copper oxide with sulphuric acid, yields with barium chloride, which is a combination of barium and chlorine, insoluble barium sulphate, a combination of barium oxide with sulphuric acid, and soluble copper chloride, a combination of copper and chlorine.
Two days more took them through Barium and Egnatia to Brundusium, where the journey ended. At this conference it was agreed that the triumvirate should continue five years longer, Antony agreeing to assist Octavius with 120 ships against Pompey, and Octavius contributing a large land force to help Antony against the Parthians.
When the lacquer is to be dried at a high temperature barium sulphate is preferable, but when it is dried at an ordinary temperature bismuth oxychloride is better. Since the lacquer is originally of a brown colour the white lacquer is not pure white, but rather greyish or yellowish.
Moreover, no salt of pentathionic acid has been prepared in a pure state. The author has succeeded in preparing barium pentathionate thus: A Wackenroder solution was about half neutralized with barium hydrate, filtered, and the clear solution evaporated in vacuo over sulphuric acid. After eighteen days crystals, which proved to be barium pentathionate + 3 molecules of water, formed.
Doubtless it is not necessary to recall here how, in December 1895, Röntgen, having wrapped in black paper a Crookes tube in action, observed that a fluorescent platinocyanide of barium screen placed in the neighbourhood, had become visible in the dark, and that a photographic plate had received an impress.
Filter through blotting paper, and to the clear filtrate add some phosphate of soda solution. A second precipitation proves the presence of magnesia. Sulphates. A solution of barium chloride and dilute hydrochloric acid gives a white turbidity. Chlorides. A solution of silver nitrate and nitric acid gives a white curdy precipitate. Test for Lead in Drinking Water.
Filter off the carbonate and wash it with hot water, testing the slightly acidified washings for sulphate and preserving any precipitates which appear in these tests. Acidify the filtrate with hydrochloric acid until just acid, bring to boiling, and slowly add hot barium chloride solution, as in the preceding determination. Add also any tests from the washings in which precipitates have appeared.
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