232. 25 c.c. of a solution, containing o'2105 gram of a copper alloy in the form of sulphates, was neutralized with Na2CO3 and then rendered acid by acetic acid; to the acidulated solution an excess of freshly prepared potassium iodide solution was added and the liberated iodine titrated by a standard Na2SO, solution; 31°29 c.c. were required for the reaction. 25 22 C.C. of the thiosulphate solution were found to be equivalent to 25 c.c. of iodine solution of which 1 c.c. = 0006313 gram of copper. Calculate the percentage amount of copper present in the alloy. 233. 0'5005 gram of a sample of calcite, was weighed out, dissolved in dilute HCI and precipitated as calcium oxalate; the washed precipitate was treated with dilute sulphuric acid and the solution titrated with potassium permanganate solution of which I c.c. = = 0.0056 gram of iron; 100'08 c.c. of the permanganate were decolorized. What was the percentage of calcium in the mineral? N 2 234. In an estimation of nitrogen by the soda-lime method, 0'2102 gram of benzamide was taken and the evolved ammonia absorbed in sulphuric acid solution, 25 c.c. being taken; the residual acid required 21'517 c.c. N of NaOH for neutralization. What was the percentage amount of nitrogen in the benzamide? 2 235. The subjoined data were obtained in an estimation of NH3 in (NH4)2SO4 by the method of distillation with soda-lime in the wet way. Weight of ammonium sulphate taken = 0 3200 gram. N 41'7 c.c. of 2 soda just neutralized the residual acid. Calculate from these data the percentage amount of ammonia in ammonium sulphate. 236. One hundred cubic centimetres of a semi-normal solution of sodium carbonate were added to 100 c.c. of a neutral solution containing copper sulphate. After filtraN tion, the residual Na,CO, was determined by means of 2 sulphuric acid, of which 27 c.c. were required. What weight of Cu SO4 in grams was present in each litre of the solution? 237. The following results, obtained in an analysis of Rochelle salt, give sufficient data for the estimation of K and Na in the sample used; find the percentage of each of these elements present. 238. From 09330 gram of a mixture of sodium chloride and iodide, o'9066 gram of sodium sulphate is obtained. What weights of the sodium chloride and sodium iodide are there in the weight of mixture taken ? 239. CALCULATE the formula of a salt containing sodium and chlorine which yielded the following numbers on analysis : (a) o'1998 gram of the salt gave o'4865 gram of silver chloride, and metallic silver. (b) o'9543 gram of the salt gave 11584 grams of sodium sulphate. 240. 03951 gram of a substance supposed to be arsenic pentoxide was dissolved in dilute ammonia, and precipitated as magnesium-ammonium-arseniate. After drying at 110° the precipitate weighed o'6544 gram. Was the substance As, O5? 241. The mineral nontronite gave on analysis the following numbers. Calculate its formula. 242. 100 grams of a mixture of potassium and sodium chlorides have furnished 164'1 grams of potassium-platinum chloride. What is the composition of the mixture? 243. Calculate the formula of thallium perchlorate from the following determination :-01831 gram of salt gave 02476 gram of the double chloride of platinum and thallium. 244. Calculate the percentage amount of chlorine contained in vanadyl trichloride of which 3'9490 grams added to 7.383 grams of silver dissolved in nitric acid required 3 cubic centimetres of centesimal HCl solution for complete precipitation according to Gay-Lussac's method. !245. Two equal volumes of a liquid found to contain an oxygen compound of bromine were completely reduced with sulphurous acid, the excess of which was removed by boiling in one portion the sulphuric acid formed was estimated as barium salt, and in the other the bromine was weighed as silver bromide. Analysis gave: weight of Ba SO4 0402 gram; weight of silver bromide, o 3240 gram. Required the composition of the oxide of bromine. 246. 12185 grams of perchloric acid yielded 1.6785 grams of dry potassium salt of this salt o'9660 gram lost o ̊444 gram on heating, and the residue required o‘744 gram of pure silver for complete precipitation. Required the percentage amount of acid contained in the quantity taken. (Roscoe.) ! 247. Required the percentage of real acid contained in 1483 grams of aqueous acetic acid, which evolved 0'427 gram of carbonic acid on adding it to bicarbonate of sodium. 248. 2122 grams of aqueous formic acid required for neutralization 36'3 cubic centimetres of soda solution, of which each cubic centimetre contained (0°9025 × 31) milligrams of soda. Required the percentage of pure acid contained in the liquid. 249. Calculate the volume of carbonic acid in 10,000 volumes of sea-air, from the following numbers, obtained by Pettenkofer's method : I cubic centimetre of oxalic acid solution = I mgrm. CO2. 50 cubic centimetres of baryta water = 55 18 cubic centimetres of oxalic acid solution. Capacity of flask used, 4815 cubic centimetres. Temp. of air 13° 9. Bar. 7531 mm. 50 cubic centimetres of baryta solution taken of this 25 cubic centimetres after the experiment required 26°29 cubic centimetres of oxalic acid solution for neutralization. 250. The following numbers express the amount of the constituents in 1,000 grams of the water of the Irish Channel : Calculate the composition of the saline matter of the water on the following assumption: That the sodium, potassium, and ammonium are combined with chlorine, the excess of chlorine being united to magnesium. The bromine and nitric acid are also to be united to the magnesium. The sulphuric acid exists in combination with lime, the excess being united to magnesia. The ferric oxide exists as ferrous carbonate. ! 251. Calculate the illuminating power of a gas flame burning 5 cubic feet per hour, expressed in candles burn ing 120 grains (7.79 grams) of sperm per hour, from the following data : 252. 05637 grams of the barium salt of an organic acid, obtained by the action of carbonic acid on C, H4 BrC2 H5 in presence of sodium, lost, on drying at 120° C., 0°0430 gram of water, and gave o°2733 gram barium sulphate. Required the formula of the salt. !253. 4826 grams of a nitrogenous organic body yielded, after heating with soda-lime, 1°532 grams of the double chloride of platinum and ammonium. Required the percentage of nitrogen contained in the organic substance. ! 254. Required the percentage composition, observed and calculated vapour density, and formula of a body which gave the following analytical results : (c) Determination of vapour density according to Gay-Lussac's method : Weight of substance employed, o'0893 gram. Temperature of the air, 8° C. Height of barometer, 739 mm. Temperature of vapour, 50° C. Volume, 46°2 cubic centimetres. |