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When no more carbonic acid is evolved, another tube from this last flask is connected with the aspirator, the pinch-cock of the pipette open, and air drawn through the apparatus for about half a minute, and thus all the carbonic acid evolved absorbed, or the flasks may be slightly heated.
"Let us have some fresh blood," he said, digging a long bodkin into his finger, and drawing off the resulting drop of blood in a chemical pipette. "Now, I add this small quantity of blood to a litre of water. You perceive that the resulting mixture has the appearance of pure water. The proportion of blood cannot be more than one in a million.
I have myself seen this being done, as I shall mention in its place. But, squeamish as I may seem, I cannot bring myself to describe what I could not endure even to continue watching. Let it suffice to say, blood obtained from a still living animal, in most cases from a human being, was run directly by means of a little pipette into the recipient canal. . . .
Others are less complicated, and also less exact, but still require quite a troublesome manipulation such, for example, as the process of Pettenkofer, as modified by Fodor, that of Hesse, etc. Montsouris Apparatus. Smith's Minimetric Apparatus. Bertin-Sans Apparatus. Bubbling Glass. Pipette. Arrangement of the U-shaped Tube. It is from such efforts that have resulted the processes of Messrs.
The Billionaire drew near, adjusted a pair of pince-nez on his hawk-like nose, and peered curiously at the apparatus. Herzog, with a quick gesture, turned a small silver faucet. "Oxygen! Unlimited oxygen!" he exclaimed. "I have found the process, gentlemen, commercially practicable. Oxygen!" Even as he spoke, a lambent, sparkling liquid began to flow through the pipette, into the flask.
"In examining red must, the method should be modified as follows: Instead of first filling the pipette with tincture of litmus, fill it with water to the line A, and transfer it into the bottle.
Fill the flask to the mark with water and shake thoroughly. Measure off 25 cc. of this semi-solution in a measuring flask, or pipette, observing the precaution that the liquid removed shall contain approximately its proportion of suspended matter. Empty the flask or pipette into a beaker and wash it out.
Pipettes are usually already graduated when purchased, but they require calibration for accurate work. PROCEDURE. Clean the pipette. Draw distilled water into it by sucking at the upper end until the water is well above the graduation mark. Quickly place the forefinger over the top of the tube, thus preventing the entrance of air and holding the water in the pipette.
You will then see the glowing of those colours over the surface of the water. On a small scale we produce them thus: A common tea-tray is filled with water, beneath the surface of which dips the end of a pipette. A beam of light falls upon the water, and is reflected by it to the screen.
Burettes may also be calibrated by drawing off the liquid in successive portions through a 5 cc. pipette which has been accurately calibrated, as a substitute for weighing.
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