202 SELECTION AND USE 



When employed as a preservative, glycerine is used either 

 pure or diluted, according to circumstances. Equal parts of 

 glycerine and water form a very excellent medium for most 

 objects. It is alleged, however, that fungi are very apt to grow 

 in glycerine and its solutions. We are inclined to believe 

 that this may be avoided by adopting the precaution detailed 

 at the end of this section. We Lave now before us specimens 

 that were mounted in pure glycerine and water, eighteen years 

 ago, and they are still quite perfect. If, however, there should 

 be any danger in this direction, the addition of a little camphor 

 will prevent the evil. Glycerine exerts a powerfully solvent 

 action on many salts, particularly salts of lime, such as the car- 

 bonate, and hence it is employed for preventing scale in the 

 boilers of steam-engines. This property renders it dangerous 

 to use it for the preservation of structures containing com- 

 pounds of lime. 



GLYCEKINE JELLY. The original directions given by Law- 

 ranee are as follows: " Take any quantity of Nelson's gelatine, 

 (any good gelatine will answer, however,) and let it soak for 

 two or three hours in cold water; pour off the superfluous 

 water, and heat the soaked gelatine until melted. To each 

 fluid ounce of the gelatine add one drachm of alcohol, and mix 

 well; then add a fluid drachm of the white of an egg. Mix 

 well while the gelatine is fluid but cool. Now boil until the 

 albumen coagulates, and the gelatine is quite clear. Filter 

 through fine flannel, and to each fluid ounce of the clarified 

 gelatine add six fluid drachms of Price's pure glycerine, and 

 mix well. For the six fluid drachms of glycerine a mixture of 

 two parts of glycerine to four of camphor water may be sub- 

 stituted." 



Glycerine jelly is a very excellent medium, and is easily used. 

 At ordinary temperatures it is quite solid, but when slightly 

 heated it melts, and may be used like balsam, directions for 

 mounting in which will be found in the next section. Objects 

 that are to be mounted in glycerine jelly should be soaked 

 until thoroughly saturated with a mixture of 7 parts glycerine, 

 6 parts water, and 1 part alcohol. It is also well, after immers- 

 ing them in the melted jelly, to place the slide for a short time 



