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T H E J O U R X A L OF I X D U S T R I A L A N D EA’GINEERING C H E M I S T R Y .
and the son learned the same trade before he came to Copenhagen. Here he first started to study with the intention of becoming a n artist, b u t soon he changed and took up scientific studies. During his years of study he had to provide for his own living by teaching school and drawing pictures and writing stories for the magazines. I n 1876 he won the University’s gold medal for a treatise on certain fungi found in manure, and a few years later he took his degree as Phil. Dr. At this time he also participated in the translation of Darwin’s books. He was first connected with the “ K y Carlsberg” brewery, b u t as soon as the Carlsberg Laboratory” (a research laboratory, founded by J. C. Jacobsen and maintained by Gamle Carlsberg ” brewery) was instituted, he was made director of one of its two departments, the physiological department, and here he worked until his death. I n the first years after his revolutionizing discoveries he met much opposition from both inside and outside Denmark, and the adversity seemed to weigh heaITily on his shoulders, b u t even the faintest mumbling has stopped long ago and Emil Chr. Hansen has received the highest honors and recognition which i t is possible to bestow on a man both from European governments and from the most important scientific bodies in the world. His discoveries brought great fortunes to others. Hansen himself got nothing but his far from royal salary, but he was satisfied with a modest living and with small trips to the great a r t galleries of Europe; during his whole life he was a passionate lover of art. Xt his death he did not leave much worldly goods, but he left a name for himself which will go down in history side b y side by the names of Louis Pasteur and Robert Koch. NIELS C. ORTVED. ‘ I
Oct., 1909
pressed in electrical units, the readings being made with a carefully calibrated rheostat. I n the application of conductivity measurements for technical purposes, such apparatus is undesirable and by the use of the “Electrotitrimeter” i t is unnecessary. The difficulty of controlling the temperature has been overcome by the use of a compensating tube filled with a solution similar to the one to be tested, and when the apparatus is used for one purpose, such as for testing sulphuric acid of a certain strength, the tube is permanently sealed to prevent changes in concentration. This tube and the test tube are kept a t the same temperature by immersing in a bath consisting of the solution which is being tested, or in another form of the apparatus the bath may be water. The compensating tube and the test tube are each provided with two platinum electrodes and these are connected in such a way that each tube represents one arm of a b‘heatstone bridge, and a high resistance calibrated wire represents
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NOTES AND CORRESPONDENCE. ELECTROTITRIMETER. The “ Electrotitrirneter” is an apparatus devised for testing the concentration of an electrolyte. I t is based upon the fact that for many acids, alkalies and salt solutions the electrical conductivity varies with the concentration sufficiently to make the electrical test a method of accurate quantitative measurement. Temperature is such a n important factor in conductivity work t h a t a thermostat is usually used and the solution to be tested is brought to a given temperature before making the reading. According to Kohlrausch’s method the results thus obtained are ex-
Fig. I
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Elaotrodes rleotroie Tubes Temperature Zpualieing Bath Bridge Reaistm39 X i r e aatteries Induotion Coil Teleph~na Fleaelver Tointar
the other two arms. By means of a telephone and induction coil, a point is found on the bridge wire which shon s the solutions in the t\To tubes to be in electrical equilibrium and any change in the concentration of the solution in the test tube causes this point to move. The nire is calibrated so as to read directly in percentage content of the solution to be tested. The apparatus shown in Fig. I represents one form in which the electrolyte to be tested flows continuously through the test tube and then around both tubes forming the temperature equalizing bath. In another form as shown in Fig. 2 , the solution to be tested is poured into the test tube, the temperature equalizing bath being water in this case. These tubes are each provided with glass stopcocks so that the solution in the compensating tube as well as in the test tube may be changed when different kinds of solutions are to be tested with the same apparatus. When i t is desired to control the strength of a product which flows continuously, a portion of the product is made to pass through the test tube, and with long connections
