CHAPTER XXII 

 CEMENTS AND VARNISHES 



500. Introduction. Two, or at most three, of the media given 

 below will certainly be found sufficient for all useful purposes. 

 For many years Lee had used only one cement (Bell's). He 

 recommended this both as a cement and varnish ; gold size may 

 be found useful for turning cells ; and Miller's caoutchouc 

 cement may be kept for occasions on which the utmost solidity 

 is required. Marine glue is only necessary for making glass cells. 



For the operations of mounting in fluids, and of making cells 

 and ringing, see Carpenter's The Microscope. 



Carpenter lays great stress on the principle that the cements or 

 varnishes used for fluid mounts should always be such as contain 

 no mixture of solid particles, for those that do always become porous 

 after a certain lapse of time. All fluid mounts should have the edges of 

 the cover carefully dried and be ringed ivith glycerin jelly before applying 

 a cement ; by this means all danger of running in is done aivay with. 

 See §§ 503 and 504. But no method yet devised will make a glycerin 

 mount absolutely permanent. 



See also Aubert, The Microscope, xi, 1891, 150, and Journ. Roy. 

 Mic. Soc, 1891, p. 692 ; Beck, The Microscope, xi, 1891, pp. .338, 368, 

 and Journ. Roy. Mic. Soc., 1892, p. 293 ; Behrens' Tabellen zum 

 Gebrauch bei mikroskopischen Arbeiten (Bruhn, Braunschweig, 1892) ; 

 RoussELET, Journ. Quek. Mic. Club, vii, 1898, p. 93 ; and as to the 

 comparative tenacity of divers cements, Behrens, Zeit. iviss. Mik., ii, 

 1885, p. 54, and Aubert, Amer. Mon. Mic. Journ., 1885, p. 227 ; Journ. 

 Roy. Mic. Soc, 1886, p. 173. Aubert places Miller's caoutchouc 

 cement at the head of the list, Lovett's cement coming half-way down, 

 and zinc white cement at the bottom, with less than one-quarter the 

 tenacity of the caoutchouc cement. 



501. Peter Gray's Sealing Medium. For glycerin and other 

 mounts : 4 jmrts anhydrous lanolin, 8 parts resin, 1 part dry 

 Canada balsam. Melt together. This forms a solid mass on 

 cooling. For circular cover-glasses a piece of metal tube of the 

 necessary diameter is heated over a Bunsen, dipped into the 

 molten mixture and applied to the cover-glass. For square 

 covers, a broad bent needle is used. (Watson's Microscope 

 Record, No. 33, 1934). 



502. Paraffin. Temporary mounts may be closed with paraffin, 

 or white wax, by applying it with a bent wire, and be made more 

 or less permanent by varnishing. 



503. Gelatin Cement (Marsh's Section-cutting, 2nd ed., p. 104). 

 Take half an ounce of Nelson's opaque gelatin, soak well in 



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