Search -
An Introduction to the Physics and Chemistry of Colloids
An Introduction to the Physics and Chemistry of Colloids Author:Emil Hatschek 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: METHODS OF DEMONSTRATING ELECTRIC CHARGE. platinum foil, which are connected by suitable leads to a couple of cells or accumulators. A drop of the liquid unde... more »r examination is placed on the slide so as to touch both electrodes and covered with a cover glass. The preparation is examined under the microscope—using one of the ultra-condensers described in the previous chapter, 30 AMOUNT OF CHARGE ON PARTICLE if necessary—and the particles are seen to travel to the anode, if negatively, or the cathode, if positively charged. Both the U-tube and the microscopic method also permit the actual charge on a particle to be measured, by observing the rate of travel and the strength of the electric- field, i.e., the difference in voltage divided by the distance of the electrodes. We need only mention here that a very large number of different materials have been so examined, and that the charge carried by a particle is very much the same in all eases. CHAPTER IV. In the preceding chapter we have fully characterised the suspensoids are systems containing the disperse phase as solid particles below a certain size, in constant movement and electrically charged. A few typical suspensoids—the gold, silver, antimony and arsenic sulphide sols—have already been referred to in the first chapter, where directions are given for preparing them. These directions have one feature in common : the metal is reduced or the sulphide produced by a suitable reaction in very dilute solution. This procedure is applicable in many cases, though not universally, and sols of silver, copper, mercury, platinum, palladium, etc., have been prepared by reducing very dilute solutions of their salts with a great variety of reducing agents, such as hydrogen, hydraxine, and hydroxylamine compounds, acrolein, ...« less