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The development of the boronbenzoin fluorescence a t microgram concentrations of boron has been investigated ; a simple, but sensitive, fluorimeter was used. The development and. decay of fluorescence intensity with time was observed in various solvents in the presence of different basic compounds.The fluorescence produced when f,ormamide and its N-derivatives are used as the solvent media is stronger than that found when ethanol is used. A glycine buffer solution of pH 12.8 is effective in producing the correct conditions for developing fluorescence with ethanol as solvent, but is not effective in the formamide series of solvents. Isopropylamine and isobu tylamine are effective bases in both ethanol and the formamide series. For a series of solvents of a given chemical type, e.g., the formamides, there may be an increase in fluorescence intensity with dielectric constant, although this is not true for the alcohols.Oxygen has a pronounced inhibiting action on the developnlent of fluorescence in ethanol, but has much less eeect in formamide. There is a linear relationship between fluorescence intensity and amount of boron present in the range studied (0.06 to 0-5 pg).THE fluorescence of the boronbenzoin complex was first noted and later used by White and his c o -~o r k e r s ~~~~~ to develop a sensitive quantitative method for determining amounts of boron from 1 pg upwards. More recently, Parker and Barnes* have demonstrated the quenching effect of oxygen on this fluorescence. Since this effect was not mentioned by the earlier workers, it was decided to study the development and stability of the boronbenzoin complex in ethanol, bearing in mind the possible de-activating effects of oxygen, and to examine other solvents in the hope of increasing the sensitivity of the reaction. APPARATUSA Siemens -Ediswan MB/D 125-watt mercury lamp was used as light source, with two Spekker H556 (Chance OX1 glass) filters to isolate the 366-mp radiation. A shutter was interposed between the lamp and the sample, so that exposure of the sample to ultra-violet light could be restricted to a few seconds while a reading was taken. Thme sample cells were standard closed fluorimeter cells (Spekker H578) of internal dimensions 4 cni high, 3.5 cm wide and 1.5 cm deep, provided with two small stoppers for excluding air from the solution.A simple direct-reading fluorimeter was constructed in the laboratory.

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Schlußfolgerung Die Bestrahlung der Stärke mit Kathodenstrahlen scheint unterhalb einer Bestrahlungsdosis von 0,5 times 106 rad keinen merklichen Abbau hervorzurufen, wie die Messung der physikalischen Eigenschaften ergab. Somit können Nahrungsmittel und Nahrungsprodukte ohne weiteres zum Zwecke der Sterilisation mit Bestrahlungsdosierungen bis zu dieser Höhe behandelt werden. Für eine Reihe von Backprodukten reicht diese Dosierung bei bestimmten Schimmelpilzen nicht aus und unter Einfluß von einigen der übrigen Komponenten wird der Geschmack beeinträchtigt (7). Oberhalb des genannten Wertes wird die Stärke selbst angegriffen und bei einer Dosis von 100 times 106 rad verliert sie alle diejenigen physikalischen Eigenschaften, die sie als Handelsware so wertvoll erscheinen lassen. Die Endprodukte stellen ein Gemisch aus reduzierenden Zuckern, Hexosen, Glucuronsäure und möglicherweise anderen Säuren von niedrigem Molekulargewicht dar.

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