We use glycerin for mounting the onion peel for the following reasons: 1. As the refractive index of Glycerine is 1.473 and it it tends to reflect light so the specimen kept looks clear under the microscope.2. Glycerine is also used to expel air bubbles which can be found between slides.

**The use of glycerin in the preparation of a slide of onion peel**

Glycerin is a commonly used mounting medium in microscopy, including the preparation of slides of onion peel. It serves several purposes in the process and enhances the quality of the microscopic observation. Below are the details of the use of glycerin in the preparation of a slide of onion peel:

**1. Preservation of the Specimen:** Glycerin acts as a preserving agent, preventing the decay or decomposition of the onion peel cells. It helps maintain the integrity of the cells by inhibiting microbial growth and enzymatic activity. This preservation ensures that the sample remains viable for a longer period and can be observed multiple times.

**2. Refractive Index Matching:** The refractive index of glycerin is similar to that of glass and biological materials, making it an ideal medium for mounting slides. When a specimen is immersed in glycerin, the refractive index of the surrounding medium matches that of the specimen, reducing the loss of light due to refraction and reflection. This refractive index matching enhances the clarity and visibility of the specimen under the microscope.

**3. Reducing Air Bubbles:** Glycerin has a viscous nature, which helps in minimizing the formation of air bubbles during slide preparation. Air bubbles can interfere with the microscopic observation by distorting the specimen or obstructing the light path. The high viscosity of glycerin allows for a smooth and even spreading of the liquid, minimizing the chances of air bubble formation.

**4. Transparency and Optical Qualities:** Glycerin has excellent optical properties, including high transparency and low light scattering. When used as a mounting medium, it allows light to pass through the specimen with minimal distortion or scattering. This transparency ensures that the details of the onion peel cells can be observed clearly and accurately.

**5. Longevity of the Slide:** Glycerin helps in preserving the slide for an extended period. It prevents the drying out of the specimen and keeps it hydrated, reducing the risk of damage or shrinkage. The longevity of the slide allows for repeated observations and comparisons, making it a valuable tool for scientific research or educational purposes.

Overall, glycerin is an essential component in the preparation of slides of onion peel due to its preservation capabilities, refractive index matching, reduction of air bubbles, optical properties, and longevity. Its use enhances the quality and longevity of the slide, enabling detailed microscopic observation of the onion peel cells.