Abstract: An apparatus for determining the size of a particle or cell within a fluid includes a sample chamber for the fluid, a flow restrictor having an orifice, a pair of electrodes disposed on opposite sides of the orifice and a signal measurer for measuring a signal representative of the impedance variation between the electrodes thereby to determine the size of a particle within the fluid passing through the orifice, and further includes a blockage detector for detecting blockage of the orifice, whether partial or complete.

Abstract: A process is described for the continuous recovery of substantially pure pentane-1,5-diol from a crude product stream (1) containing pentane-1,5-diol and &dgr;-valerolactone. The feed stream (1) is continuously supplied to a vaporization zone (2) maintained under temperature and pressure conditions effective for the vaporization of pentane-1,5-diol and conducive to the thermal decomposition of reaction products of &dgr;-valerolactone thereby to form a vaporous stream. The resulting vaporous stream is continuously supplied to an intermediate section of a distillation zone (4). A reflux stream (5) of dimethyl glutarate is fed to an upper section of the distillation zone (4) and an overhead vapor product stream (8) comprising &dgr;-valerolactone and dimethyl glutarate is taken. Also an intermediate stream (11) comprising substantially pure pentane-1,5-diol is taken from the distillation zone (4), while from the bottom section of the distillation zone there is recovered a bottoms product (12).

Abstract: A process for the production of at least one C4 compound selected from 1,4-butanediol, gamma-butyrolactone and tetrahydrofuran, in which a solution of maleic anhydride in a high boiling ester is esterified with a C1 to C4 alcohol to form the corresponding maleate ester which is hydrogenated to form the at least one C4 compound. The specified high boiling ester has a boiling point which is about 30 degrees C. higher than that of the di-(C1-C4 alkyl)maleate.

Abstract: The invention provides a process for the purification of a butane-1,4-diol feed containing a minor amount of the cyclic acetal, 2-(4'-hydroxybutoxy)-tetrahydrofuran, which comprises hydrogenating the butane-1,4-diol feed in a hydrogenation zone in the presence of a minor amount of water and a hydrogenation catalyst, and recovering from the hydrogenation zone a butane-1,4-diol product that has a reduced 2-(4'-hydroxybutoxy)-tetrahydrofuran content compared with the butane-1,4-diol feed.

Abstract: A process for the production of at least one C.sub.4 compound selected from butane-1,4-diol, .gamma.-butyrolactone and tetrahydrofuran comprises contacting a vaporous stream containing maleic anhydride vapour, water vapour, and carbon oxides in an absorption zone with a high boiling organic solvent thereby to form a solution of maleic anhydride in the high boiling organic solvent. Maleic anhydride in this solution is reacted under esterification conditions in an esterification zone with a C.sub.1 to C.sub.4 alkanol to form a solution of the corresponding di-(C.sub.1 to C.sub.4 alkyl) maleate in the high boiling solvent. This solution of the di-(C.sub.1 to C.sub.4 alkyl) maleate in the high boiling solvent is contacted with a gaseous stream containing hydrogen thereby to strip di-(C.sub.1 to C.sub.4 alkyl) maleate therefrom and to form a vaporous stream comprising hydrogen and di-(C.sub.1 to C.sub.4 alkyl) maleate.

Abstract: A process is described for the production of at least one C.sub.4 compound selected from butane-1,4-diol, .gamma.-butyrolactone and tetrahydrofuran, which includes the step of hydrogenation in the vapour phase of maleic anhydride in the presence of a heterogeneous hydrogenation catalyst, which process comprises:(a) contacting a vaporous stream containing maleic anhydride vapour, water vapour, and carbon oxides in an absorption zone with a high boiling organic solvent having a boiling point at atmospheric pressure which is at least about 30.degree. C.