Glycerol Preservatives
Glycerol (glycerine) is easily available at a reasonable price and has little chemical effect on tissues. It raises the refractive index somewhat, but that is not necessarily a defect as it may enable structures to be seen within the tissue – lymph nodes, for instance.
At its simplest glycerol can be used as a simple solution in water or as 100% glycerol. The tissues can be dehydrated with increasing concentrations of glycerol in a manner similar to dehydration with increasing concentrations of ethanol, stopping when the final concentration wanted is reached. The tissue can then be stored for extended periods. There is no real need to replace the glycerol, but it should be appreciated that concentrations less than 100% may preserve less well than absolute glycerol due to the presence of water. At higher concentrations of glycerol some lipids may be removed. Triglycerides are glycerol and fatty acid compounds, after all. If the glycerol becomes dirty or greasy, then the solution and container should be changed.
There are many formulations of preservatives containing glycerol and they may contain ethanol, formaldehyde, and acids. Many of these were designed for coverslipping rather than displaying specimens, which is better done using Kaiserling fluid, but since they do not harden the coverslip will need to be sealed if a degree of permanence is required.
The lists of formulas below is by no means exhaustive. There are dozens of such mixtures and those interested should read the text listed as the reference. In all cases in the formula lists:–
| Ethanol Formalin Acetic Nitric Numbers |
refers to 95% ethanol refers to strong formalin refers to glacial acetic acid refers to concentrated nitric acid refer to millilitres of each ingredient |
| Name | Water | Ethanol | Glycerol |
| Caberla | 30 | 20 | 10 |
| Langeron | 50 | 20 | 30 |
| Gatenby & Painter | 50 | 25 | 25 |
| Hantzch | 60 | 30 | 10 |
| Silvester | 42 | 16 | 42 |
| Name | Water | Ethanol | Glycerol | Formalin | Acetic | Nitric |
| Cole | 30 | 30 | 30 | – | 0.3 | – |
| Morgenthaler | 27 | 60 | 5 | – | 8 | – |
| Newmarch | 70 | – | 25 | 5 | – | – |
| Robin | 20 | 40 | 40 | – | 4.5 | 2 |
Reference
Gray, Peter. (1954)
The Microtomist's Formulary and Guide. Chapter 17, pp. 175.
Originally published by:– The Blakiston Co.
Republished by:– Robert E. Krieger Publishing Co.
