Abstract: A duct that preferably includes a low loss inlet section is configured to include one or more flow limiting passages that extend through a portion of the low loss inlet section. The flow limiting passages are located and configured such that in the desired operating flow range of the duct, the fluid exiting the flow limiting passages has minimal effect on fluid flow into and through the duct. However, at relatively high pressure ratios, the fluid exiting the flow limiting passages will disturb the fluid entering the duct, causing mixing and shock losses, which will limit the fluid flow rate into and through the duct.

Abstract: Compounds of the general formula ##STR1## are cyclized to the corresponding isothiazolinone using a carbonyl halide of the formula RCOX where R is halogen or alkyl and X is halogen. R.sup.3 and R.sup.4 are preferably such as to form a 5 or 6 membered ring. Useful carbonyl halides are phosgene and propionyl chloride. Using acyl halides such as propionyl chloride, a mixture of the isothiazolinone and a salt of the carboxylic acid can be obtained, for example an essentially equimolar mixture of 2-methyl-4,5-trimethyl-4-isothiazolin-3-one and sodium propionate.

Abstract: Compounds of the general formula ##STR1## are cyclised to the corresponding isothiazolinone using a carbonyl halide of the formula RCOX where R is halogen or alkyl and X is halogen. R.sup.3 and R.sup.4 are preferably such as to form a 5 or 6 membered ring. Useful carbonyl halides are phosgene and propionyl chloride.