Abstract: Method of working, forming, and finishing single crystals which are able to sublimate. The single crystal is acted upon by an instrument the temperature of which is the same or higher than the temperature at which the single crystal sublimates.

Abstract: A new compound, 1,4-diacyloxy-2,3-butanediol, having the general formula ##EQU1## where R is hydrogen atom or methyl group. The compound can be used above all as a crosslinking agent in the preparation of crosslinked hydrophilic polymeric gels. This compound can be prepared by opening the epoxy ring in such a way, that 1 mole of 1,2-3,4-diepoxybutane is treated with 2 moles of unsaturated acid of the general formula ##EQU2## where R has the aforementioned meaning.

Abstract: There is disclosed a method of preparing hydrophilic copolymers of acrylonitrile by initially polymerizing acrylonitrile with about 0.01 to about 30% by weight of a monomer selected from the group consisting of acrylamide; methacrylamide; monomers of the formula CH.sub.2 =CRCONHR.sup.1 wherein R is hydrogen or methyl and R.sup.1 is hydrogen, methyl or ethyl; N,N-dialkylacrylamides and methacrylamides and N-alkylol amides, thereafter subjecting said copolymer to hydrolysis by an aqueous acidic solvent for the monomers or swelling agent for the polymer comprising at least one compound selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, zinc chloride and zinc chloride/HCl mixtures and subsequent isolating the product thus formed by removal of the acidic hydrolytic agent therefrom.

Abstract: Arrangement for measuring, checking and control of the position of chosen points of objects with respect to an optical aiming line, which optical aiming line is determined as a connecting line between the center of an optical system of a transmitter of a light measuring beam and of the center of an optical system of a receiver, selectively sensitive to the wavelength and modulation of the light measuring beam. The position of the body with respect to this optical aiming line is determined by the screening of the light measuring beam by means of circumference of this body or by means of the edge of a screen connected with this body. A substantial feature of this invention is the application of directional optical slot systems both for the transmitter and for the receiver selection of proper sizes of outlet slots of these optical slot systems.

Abstract: A method of preparing polyamides by anionic polymerization of cyclic lactams which comprises polymerizing at least one such lactam in the presence of at least one co-catalyst selected from the group consisting of N-substituted 1,3-oxazines, 1,3-thiazines, trioxopiperidines and thiodioxopiperidines.