Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER IV APPARATUS FOR EXACT GAS ANALYSIS WITH MERCURY AS THE CONFINING LIQUID General Remarks On account of the solubility of gases in water and in the reagents, no great accuracy is attainable, even when these liquids are saturated with the gas mixture being analysed. If very accurate results are desired, the apparatus must unquestionably be filled with mercury. A few years ago it was difficult to obtain glass stopcocks which were perfectly tight, but the manufacture of glass apparatus has been so greatly improved of late that satisfactory instruments can now easily be procured. Complete certainty that the apparatus is absolutely tight can, however, be obtained only by the use of apparatus which contains no stopcocks or rubber connections whatever, and in which all openings are closed by fusing the glass tubes together. A. Apparatus With Rubber Connections And Glass Stopcocks I. Gas Burettes with Correction for Variations in Temperature and Barometric Pressure Petterssonl was the first to show that by means of a tube enclosing a volume of gas it is easy to compensate the error which would result from variations in the pressure and temperature of the atmosphere. Extreme accuracy in gas analysis can be obtained by the use of apparatus filled with mercury, and provided with such a compensating tube, the results with such an instrument being quite as exact as those obtained with the more elaborate apparatus for exact gas analysis described on p. 79, provided always that the stopcocks and rubber connections are perfectly tight. Three different forms of gas apparatus with temperature and pressure correction are shown in Fig. 36, the measuring tubes being varied to accommodate gas volumes of different sizes. Figure 36, I, shows the apparatus intended for the measure... --This text refers to the Paperback edition.