Laboratory Glass-Working for Scientists - Sciencemadness Dot Org

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GLASS-WORKING EQUIPMENT grading is done by shaking the emery with water and leaving the suspension to stand. After a specified time the liquid suspension is removed and dried, so the longer the standing time the finer the emery. Emery can also be graded by particle size, by giving the size of a mesh which will just retain the particles. A 100-mesh sieve, for example, has 100 square holes per linear inch. (Often in a sieve only about 25 per cent of the area consists of holes; the remainder is the wire network. The wire size is equal to the aperture size when 25 per cent of the sieve area is holes.) When grinding glass with increasingly fine grades of emery it is essential to clean it so as to remove the coarser emery before using the finer. The glass is ground with emery in water either on a metal former or, when flat surfaces are required, on another flat piece of glass, with the emery between the two glass surfaces. Carborundum is used mainly for fast work when much glass needs to be removed, and for grinding quartz. It is cheaper and harder than emery. It can be graded by particle size; the coarsest normally used is 90 mesh. The medium size is about 180 mesh, and the fine about 300 mesh, with very fine of 600 and 900 mesh; this last is usually unnecessary since better results can be obtained with jeweller's rouge. Carborundum is also often graded in F numbers: F consists of 240 mesh and finer; 2F of 280 and finer; and 3F of 320 mesh and finer. Carborundum is used in the same way as emery, and has the advantage that carborundum wheels and blocks can be obtained. Corundum or alumina is again faster than emery, but it is much more expensive. Finally, diamond powder can be used, and is very fast but by far the most expensive. Once the glass has been ground it can be polished with jeweller's rouge or Cerirouge (see p. 83). With these polishes an optical finish may be obtained. Glass Holders One often needs to manipulate a piece of tubing so short that the normal method cannot be employed because the glass becomes too hot to hold. Various types of holder can be used. A rubber bung, covered with asbestos paper and bored with one hole containing a glass rod or tube, can be inserted into the tube as in FIGURE 9, /. Asbestos paper can be wrapped round a small tube until it fits into the tube to be worked (FIGURE 9, //). The smaller tube may now be manipulated with comfort and hence any desired operation can be performed on the larger tube. A variation of these methods is to employ a glass holder of the type shown in FIGURE 9, //I. The holder is made by joining a small tube to a large tube; the two tubes must be coaxial. The large tubing is then cut about 2 inches from the joint 40
GLASS HOLDERS In use, the tube to be worked is wound with asbestos paper and fitted into the large tube of the holder; a rubber bung can often be used instead of the paper. Holders for spherical glass bulbs are mentioned on p. 32. BARK. and ANHORN (1949) give many examples of the use of holders of the type of FIGURE 9, ///; in many laboratories, however, they are rarely or never used. r Asbestos paper Asbestos paper m n FIGURE 9. Some ways of holding glass tubes Large Tube Supports Large tubing is often too heavy to rotate as well as support with the left hand, so a support is used to take some of the weight. The very simple device shown in FIGURE 10 consists of a piece of wood with a *V cut in the top, and a slit to let a thumb-screw slide up and down. FIGURE 10. A support for large tubing It is fixed to the stand by the thumb-screw so that the height can be varied. A few freely rotating wooden balls (e.g. small atom models) can be fixed along the *V* to increase the ease of rotation. A clamp 41 n
Page 1 and 2: FOREWORD ACKNOWLEDGEM ENTS PREFACE
Page 3 and 4: CONTENTS Grinding glass Releasing f
Page 5: ACKNOWLEDGEMENTS We thank the follo
Page 8 and 9: PREFACE scattered in the literature
Page 10 and 11: INTRODUCTION ready outgassing on ba
Page 12 and 13: INTRODUCTION in succession broke th
Page 14 and 15: INTRODUCTION MOREY, G. W., 1938, Th
Page 16 and 17: PHYSICAL AND CHEMICAL PROPERTIES OF
Page 30 and 31: Pyrex PHYSICAL AND CHEMICAL PROPERT
Page 36 and 37: GLASS-WORKING EQUIPMENT 3 The Glass
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Chapter 5 THE MANIPULATION OF LARG
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THE MANIPULATION OF LARGE TUBING th
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THE MANIPULATION OF LARGE TUBING ro
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THE MANIPULATION OF LARGE TUBING jo
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SOME OPERATIONS WITH A GLASS-WORKIN
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SOME OPERATIONS WITH A GLASS-WORKIN
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Chapter 7 METAL-TO-GLASS SEALS ALTH
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METAL-TO-GLASS SEALS The finished b
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METAL-TO-GLASS SEALS Multiple Wire
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METAL-TO-GLASS SEALS will not be le
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METAL-TO-GLASS SEALS but in either
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METAL-TO-GLASS SEALS 29 per cent Ni
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METAL-TO-GLASS SEALS hard glasses i
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METAL-TO-GLASS SEALS Glass tubing m
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SOME TYPICAL SINGLE PIECES OF EQUIP
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Chapter 9 THE ASSEMBLY OF COMPLEX A
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THE ASSEMBLY OF COMPLEX APPARATUS d
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THE ASSEMBLY OF COMPLEX APPARATUS d
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THE ASSEMBLY OF COMPLEX APPARATUS u
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THE MANIPULATION OF SILICA with a f
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THE MANIPULATION OF SILICA surface
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Anhorn, V. J., 5, 28, 41, 47, 123,
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Abrasives, 39 Alkaline attack on gl
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Lead glass, 23,108 Lead glass compo
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Laboratory Glass-Working for Scientists - Sciencemadness Dot Org

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