What is the chimney effect and how does it affect distillation efficiency?
By evaporation - changing of state from liquid to gas - the volume of the sample increases by a factor up to 20,000. In the condenser the gas is re-condensed to a liquid and the volume shrinks immediately. During this evaporation-condensation process, vapor velocity at narrow points of the glass apparatus can be up to 150 km/h.
Distillation efficiency can be significantly increased by reducing the so-called chimney effect.
In order to maximize turbulence inside the condenser, the vacuum is applied at the top middle, however, the vacuum connectors are below. This optimal construction maximizes the movement of vapor inside the condenser, thus preventing fumes escaping to the vacuum source.
Can the evaporation flask be fed via the condenser stopcock?
Yes, all condensers used for R-210, R-215 and R-3 allow feeding of the evaporation flask through the standard stopcock. The C- and A-condenser for R II consist of a screw-cap instead of a stopcock and therefore does not allow feeding, a stopcock for feeding is optionally available.
Are the condensers shown on the previous page compatible with the entire current generation of BUCHI Rotavapor® product lines (R-215, R-210, R II, R-3)?
Yes, the glass assemblies V, C and A are compatible with the current generation BUCHI Rotavapor®. Glass assemblies CR, S, E and BY are compatible with the product lines R-210 / R-215 and R II only. It is recommended to also obtain a support rod (condenser holder) for glass assemblies V, C, CR, S and BY.
What factors influence glass shock temperature?
DURAN® borosilicate glass 3.3 is notable for its excellent temperature stability. The shock temperature is influenced by many stress factors which act cumulatively. Typical factors are tensions, vacuum, mechanical damage and shape as well as thickness of the respective glass part. Glass should be inspected visually prior to any use, especially when applying vacuums.
Are there differences between BUCHI and 3rd party evaporating flasks?
Yes, there may be several properties which set high quality BUCHI flasks apart: Optimized/uniform flask thickness, quality of joints and sphericity of the flask. All of these properties have an important impact on distillation efficiency.
What do the numbers “29/32” shown on previous pages mean?
The number-pair (e.g. 29/32) describes a joint size. The first number refers to the width of the joint (A). The second number (after the slash) refers to the length of the joint (B). 29/32 therefore means that the width of the joint is 29 mm and the length of the joint is 32 mm.
Can BUCHI provide customized glassware which is not listed in this document?
Yes, there is an additional extensive range of glassware available. BUCHI also offers customized glass according to your needs, for example amber glass for light-sensitive samples. For further information about our glassware range please contact your local BUCHI representative.
