The lifetimes of fluorescent substances are determined by exciting the fluorescence with light modulated at a high frequency and measuring the difference in phase between the exciting light and the resulting fluorescence. The exciting light is modulated by an ultrasonic standing wave in a liquid which causes the latter to act as an intermittent diffraction grating. Photomultiplier tubes are used to pick up the exciting and fluorescent light. Tuned circuits are used to isolate a single harmonic of the signal from the phototub~s and the phase shift determined by comparison with a calibrated phase shifting circuit. The phase angle q,isrelated to the lifetime bytanq,=wT. In whichw is 2,.. times the frequency of modulation and T is the lifetime of the excited state. The data show that lifetimes can be determined with a precision of 1 to 2X 10-10 second.The lifetimes of acridone in neutral solution (saturated to 10 percent saturated) and quinine sulfate (4X 10-6 to 4X 10-o M) in 0.01 M nitric acid are independent of the concentration. The values found are acridone 1.59±0.01XlO-s second, and quinine sulfate 2.28XO.02XlO-s second. The lifetime of fluorescein in 0.OO5M potassium hydroxide increases with concentration over the range 10-6 to 5X lO-4M. This fact can be explained by assuming that some of the fluorescent light is absorbed and re-emitted. The lifetime of fluorescein extrapolated to zero concentration is 4.5±0.lX10-9 second.
A common method for the preparation of hydroxylamine has been to pass sulfur dioxide gas slowly into a cold mixture of sodium nitrite and sodium carbonate in water until the solution is just acid to litmus.1 The hydroxylamine disulfonate ion formed by this process was hydrolyzed by heating the solution, which was then evaporated to dryness and the hydroxylamine extracted as either the sulfate or chloride. The following equations represent the two steps N02-+ 2HS03-+ H+ = H0N(S03)2-+ h2o H0N(S03)2" + 2H20 = HONH3+ + 2SOr + H +
the sulfuric acid-malic acid complex. The inhibitor thus decreases the concentration of the complex and thereby slows down the reaction.The explanation for the maximum appears to be the same as for the other acids mentioned i. e., there exists an equilibrium, H2SO4 SO3 +
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