STIEDA'S WHITE ZINC CEMENT. 257 



447. Amber and Copal Varnish (HEYDENREICH, Zeit. f. iviss. 

 Mik., 1885, p. 338). An extremely complicated mode of 

 preparation. The varnish may be obtained from Ludwig 

 Marx, at 110, Moskowskaja Sastawa, St. Petersburg; or 79, 

 Gaden, Vienna ; or 1, Romerthal, Mayence. 



448. Shellac Varnish (BEALE, p. 28). Shellac should be_ 

 broken into small pieces, placed in a bottle with spirit of 

 wine, and frequently shaken until a thick solution is obtained. 

 The Micro. Dictionary says that the addition of 20 drops of 

 castor oil to the ounce is an improvement. 



Untrustworthy, but useful for protecting balsam mounts 

 from the action of oil of cedar. 



For a method of preparing chemically pure shellac (a some- 

 what important matter), see WITT, Zeit. f. wiss. Mik., 1886, 

 p. 199. 



For SEAMAN'S shellac cement for attaching metal to glass, 

 see Journ. Roy. Mic. Soc., 1888, p. 520. 



449. Sealing-wax Varnish (Micro. Diet., " Cements "). Add 

 enough spirit of wine to cover coarsely powdered sealing-wax, 

 and digest at a gentle heat. This should only be used as a 

 varnish, never as a cement, as it is apt to become brittle and 

 to lose its hold upon glass after a time. 



450. Tolu Balsam Cement (CAKNOY'S Biol. Cell., p. 129). 

 Tolu balsam . . . . .2 parts. 

 Canada balsam . . . . .1 part. 

 Saturated solution of shellac in chlo- 

 roform ...... 2 parts. 



Add enough chloroform to bring the mixture to a syrupy 

 consistence. Carnoy finds this cement superior to all others. 



451. Stieda's White Zinc Cement (Arch. f. mik. Anat., 1866, 

 p. 435). Rub up oxide of zinc with turpentine, and add, 

 stirring continually, for every drachm of the zinc oxide 1 

 ounce of a solution of damar in turpentine (of the consist- 

 ency of thick syrup) . This gives a white cement like Ziegler's. 

 For a red cement take, instead of zinc, cinnabar, and take 2 

 drms. of the metal for each ounce of the damar solution. 

 If the cement has become too thick with age, dilute with 

 turpentine, ether, or chloroform. 



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