摘要:
In a new and improved process for preparing high-purity nitric acid by distillation or rectification of nitric acid, crude nitric acid or mixtures thereof in a column, 85-95% strength by weight nitric acid, crude nitric acid or a mixture thereof is distilled at from 70 to 110° C. and a pressure of from 0.1 to 2 bar.
摘要:
A method of boring a tunnel with a tunnel boring machine comprising injecting into the formation to be bored just before the cutting tools of the boring machine and optionally into the internal discharge chamber of the boring machine, an aqueous foam containing at least one clay, at least one surfactant and at least one gas in proportion to produce a good quality, stable foam with the formation material and discharging the material from the tunnel via the discharge of the boring machine.