Ground glass joint
A ground glass stopper is a cone-shaped ground glass stopper, in which the outer surface of the cone is roughened to ensure a better grip and a denser complete. It is used for sealing glassware and vessels such as flasks, round bottom flasks or laboratory bottles. The ground stopper together with its polished inner part - the core - the counterpart to the ground outer part - the sleeve - the vessel. Both parts together a glass - on-glass closure dar. this Lock is used, and others with standing or storage vessels in the chemical sector, often in liquid or crystalline, and in particular for aggressive substances that attack other cover forms or would dissolve. Through joint grease the tightness of the closure can be improved. Ground joints or - stuff are not suitable for strong alkalis, as these may damage the glass surface.
As a rule, correspond to conical joints and associated plug a general equipment standards. One then speaks of a standard ground or standard ground (abbreviated NS). Ground joints have a defined slope of 1:10. If a vessel or equipment damaged with standard ground joint, the upper part can be " blown " by a glassblower and glass apparatus builders to a new vessel, thus saving the initial purchase of the expensive device.
Designs
-Stoppered glass exist in two main types, solid plug and hollow stopper.
Solid plugs are made of a glass rod, which is heated and shaped by compression molding into a glass blank that already includes the unit in a Rohkern and handle the plug. In a further step, the actual standard ground is generated on the core of the plug by grinding.
Hollow plugs are available with conical bottom or flat bottom, they are made of glass tubing, which is dissolved by heating in the viscous state and then injected manually from a glassblower in a plug form. Hollow plugs are characterized by a significantly lower weight, are in production, however, much more complex and thus more expensive. Also hollow stopper form the core of the handle and ground stopper. The core is replaced as in the solid plugs his standard ground in the grinding.
Conical ground stopper, there are also made of polypropylene ( PP) hollow with sealing rings up to size NS 29/ 32, and the sizes NS 34/35, NS 45/40 and NS 60/46 PE-LD. They can be autoclaved (121 ° C). Furthermore, polytetrafluoroethylene ( PTFE), solid with sealing rings. They are temperature resistant up to 270 ° C and NS are in the standard ground joint sizes 10/19, 14 /23, 19/26, 24/29, 29/32 and 34/35 available.
Plug sizes according to DIN 12254 are:
- NS 7 /16, 10/19, 12/ 21, 14 /23, 19/26, 24/29, 29/32
- NS 34/35 and NS 45 /40 ( not according to DIN )