Types of ground glass joints

AU ground glass joints should be constructed of a high resistance glass, such as Pyrex. The most common form is shown in Fig. II, 55, 1, and this is the type largely encountered in practice. Fig. II, 55, 2 is 

The spherical joint or semi-ball joint or ball and socket joint is illustrated in Fig. 11, 55, 7, which includes one type of special clamp for holding the two halves of the joint together. This connexion cannot freeze 

Size Designation Nominal Diameter OF Ground llEMISPlIEllE Nominal Diameter AT Upper End of Ground Zone Nominal Bore 

These dimensions were supplied by Quickfit and Quartz Ltd. 

Semi-Ball Size Ball Diameter mm. Tube, Bore mm. Semi-Ball Size Ball Diameter mm. Tube, Bore mm. 

APPARATUS WITH INTERCHANGEABLE GROUND GLASS JOINTS SUITABLE FOR GENERAL USE IN PREPARATIVE ORGANIC CHEMISTRY 

The spherical or semi-ball joint is shown in Fig. 2.6 which includes one type of special clamp for holding the two halves of the joint together. This connection cannot freeze or stick (as conical joints sometimes do) and it introduces a degree of flexibility into the apparatus in which it is used. The area of contact between the ground surfaces is relatively small so the joints are not intended to provide for considerable angular deflection. The main application is in conjunction with conical joints rather than as a substitute for them. The conical-spherical adapters shown in Fig. 2.7 provide a means of inserting a spherical joint while retaining the conical joint principle. 

Precision made stopcocks, with interchangeable ground glass keys, are usually fitted with key retainers to prevent accidental loss or breakage during storage and use. 

Provided adequate care is exercised to use only joints that fit well, and the ground surfaces are suitably lubricated and parted after use while still warm, sticking will rarely occur. If, however, a ground joint should seize up or freeze the following suggestions may be found useful  

Set the joint in a vertical position and apply a layer of glycerine or penetrating oil to the upper surface. The glycerine will slowly penetrate into the joint, thus permitting the separation of the ground surfaces. 

If procedure (1) is unsuccessful, direct a stream of hot air from a blower on to the outer surface of the joint for a few seconds and gently draw the members apart with a twisting action gentle tapping on the edge of a wooden bench is sometimes helpful. 

---

As illustrated (Figs 2.1 and 2.6), the types of ground glass joints which are manufactured to precise specifications are either conical joints or spherical joints respectively. 

The standard DIN 12242 specifies types of ground-glass joints and their applications in laboratory apparatus. The sizes of the interchangeable standard joints (conical, 1 10) are covered by TGL 14972, sheet No. 2, and DIN 12242. Laboratory apparatus is equipped with joints of series 1 and 2, of which specimens 14.5/23, 29/32... 

E. Miscellaneous Tubing Connectors. The variety of tubing couplers is enormous and a comprehensive list would be out of place in this book, but several additional types will be mentioned here which are useful in the laboratory. Metal standard taper and metal ball joints are available, and these will mate with corresponding ground-glass joints to provide one means of connecting parts made of dissimilar materials.4 As with glass standard taper joints, the seal is... 

---