GAS FACTS published periodically for analytical chemists
were observed t o have activ ity. In an anhydrous system the reaction was found to be significantly affected by 0-5 ppmv oxygen. For example, CO interaction with such traces of oxygen accel metal surfaces erated the FeO-catalyzed conversion of CO from 1.80 For many years it's been suspected that low concentra to 13.09%/year. Interest ingly, an increase in oxygen tions (20 ppmv) of carbon monoxide reacted unpredict concentration in the FeO system to 30 ppmv then ably with steel cylinder sur faces. Measurements carried decreased the reaction rate to a loss of 2.97%/year. out at Scott have shown It was hypothesized that at that the reaction proceeds at room temperature. It was the higher concentration.
Ε 20.06Q. „^
3rlC
c
n
„
^^ • ·
Extension of Accessible First-Order Rate Constants and Accurate Dead-Time Determinations for Stopped-Flow Spectroscopy 3153 First-order rate constants as large as 2 Χ 103 s'1 can be determined. Stopped-flow instrument dead times are determined by a phenomenological method. Peter N. Dickson and Dale W. Margerum*, Department of Chemistry, Purdue University, West Lafayette, Ind. 47907 Anal. Chem., 58 (1986) Chemical Procedure for Preparing Surface-Enhanced Raman Scattering Active Silver Films 3159 Silver films provide an enhancement factor of 105 for 4,4 / -bipyridine. The detection limit is 10~7 M with good linearity in concentration vs. signal intensity over 3 orders of magnitude. Fan Ni and Thérèse M. Cotton*, Department of Chemistry, University of Nebraska—Lincoln, Lincoln, Neb. 68588-0304 Anal. Chem., 58 (1986) Development of a Microdroplet Mixing Technique for the Study of Rapid Reactions by Raman Spectroscopy 3163 The technique is based on the collision and subsequent coalescence of two highly reproducible streams of microdroplets. The stream then passes through an argon ion laser beam. Stanley F. Simpson, James R. Kincaid*, and F. James Holler*, Department of Chemistry, University of Kentucky, Lexington, Ky. 40506 Anal. Chem., 58 (1986)
• •
"£
^J»
" υ
• Γ
Briefs
b0
0
'•'
ιΟ
?
3 10
ime ( ioys )
Loss of CO in untreated steel cylinders. Linear least squares fit.
found too that the rate varies significantly from cylinder to cylinder. Batches of 20 cylin ders showed concentration losses ranging from < 1 % to >5%/year. Mean con centration change was -1.07%/year. Good agreement was found between CO loss and C02 formation. Eg, loss of CO of 0.188 ppmv/year was off set by C02 formation of 0.200 ppmv/year. The reac tion was determined to involve various metal oxides on the inner surface of the cylinders. All the iron oxides
oxygen competed for active sites on the metal oxide sur face, hindering adsorption of CO. When water was intro duced into the system, FeO activity was reduced so CO loss was only 0.09%/year. Scott has developed unique cylinder wall treat ments to reduce CO losses to
