TECHNICAL INFORMATION
408
Care and Handling of Volumetric Glassware
GLASS VOLUMETRIC APPARATUS Glass volumetric apparatus comprises a class of objects used to measure volume. These volumes are indicated by lines in or on the outer surface of the glass produced by etching with hydrofluoric acid, by engraving with a thin wheel or abrasive blast, by applying a staining material which colors a thin layer of the glass when heat is applied, or by application of an enamel which is fused on the glass without etching. Etched and engraved lines are usually colored by filling them with a fused-on glass enamel or by staining. The development of more durable and compatible stains and enamels has encouraged producers to favor these methods over the “etched and filled” method, thus reducing safety hazards to production workers involved in the acid etching process. In addition to the lines indicating the volumes, the numerical values of these volumes in the particular system of weights and measures used also must be marked on the apparatus (Fig. 2-C). The temperature of calibration (Fig. 2-B) also usually appears on the instruments since the volume of a glass vessel changes slightly with temperature. Finally, the method of use — whether calibrated to contain or to deliver the indicated volume — generally is marked either as “contains” or “delivers,” or more frequently as “TC” or “TD” (Fig.2-A). The International Standards Organization designation for “contains” is “IN” and “delivers” is “EX”. Some United States manufacturers are currently adopting this international designation. Some pipets (Fig. 3) are calibrated to deliver the indicated volume when the small amount remaining in the tip after free delivery has ceased is blown out and added to the main delivery. These pipets sometimes are said to be “calibrated for blowout.” To call attention to this method of calibration, two lines with the words “blow out” above them are printed near the top. A color-coded size and/or subdivision identity band is found just below the top end of the pipet. This band is to aid in sorting and selection of the pipet; however, a final check of the printed capacity and subdivision should always be made to minimize the possibility of errors. KIMBLE GLASSES FOR VOLUMETRIC APPARATUS KIMAX ® 33 expansion borosilicate glass 33 expansion borosilicate glass glass is a borosilicate composition with low coefficient of expansion. Consequently, apparatus made of it can have heavy walls to minimize mechanical breakage, and still possess high resistance to thermal shock. KIMAX® 33 expansion borosilicate glass also has very high resistance against chemical attack. It is a borosilicate glass meeting the requirements for the Type I, Class A glass of American Society of Testing and Materials — E438. The alkali content is low and it is made without elements of the calcium, magnesium, and zinc groups or the heavy metals. The combined total of arsenic and antimony oxides is less than 0.005%. Volumetric apparatus made of 33 expansion 51 expansion borosilicate glass is also a borosilicate composition with the best all-around chemical durability of available commercial glasses; and because of a comparatively low coefficient of expansion, it also possesses good resistance to heat shock. 51 expansion borosilicate glass meets the requirements for the Type I, Class B glass of ASTM-E438. Apparatus made of this glass is trademarked KIMAX-51® and liquids contained in apparatus made of the glass. borosilicate glass is trademarked KIMAX®. Kimble ® 51 expansion borosilicate glass
Fig. 2
Fig. 3
Indicates “Calibrated For Blowout”
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B
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