LEARNING OBJECTIVE: Identify commonly used pharmaceutical instruments and describe the purpose of each.

In the process of preparing some pharmaceutical preparations, you may need to use specialized instruments. To acquaint you with some of the more commonly used pharmaceutical instruments, the following sections will give you a description of each instrument and explain its purpose. See figure 6-2 for an illustration of each instrument discussed.

Pharmaceutical Balances
Two types of pharmaceutical balances are in common use in the Navy: torsion balances (shown in figure 6-2) and electronic balances (not shown). These balances are classified as either "Class A" or "Class B." Class Abalances are used for weighing loads from 120 mg to 120 g. All dispensing pharmacies are required to have at least one Class Abalance on hand at style="mso-spacerun: yes"> all times. Class B balances weigh loads of more than 648 mg, and they must be conspicuously marked "Class B." Class B balances are optional equipment in the pharmacy.

Ribbed Funnel
Ribbed funnels are utensils used in the filtering process. They are most commonly made of glass, but other substances (tin, copper, rubber) are occasionally used. The funnel is shaped so that the inside surface tapers at a 60 E angle, ending in a tapered delivery spout. The inside surface is "ribbed" to allow air to escape from between the glass and the filtering medium (improving the filtration process).

Erlenmeyer Flask
The Erlenmeyer flask is a glass container with metric measurements inscribed on it. It is used for mixing and measuring various medicinal ingredients.

Mortar and Pestle
These two items always go together, one being useless without the other. The mortar is basically a heavy bowl, with one distinct property: the inside concavity is geometrically hemispheric. The accompanying pestle is primarily a handtool that has a tip made of identical material as the mortar, and its convexity forms a perfect hemisphere. The reason for the two opposing hemispheres is to provide an even grinding surface. Mortars and pestles are made of glass, metal, or unglazed pottery called wedgewood. Glass is used when triturating (reducing substances to fine particles or powder by rubbing or grinding) very pure products (such as eye ointments), and when the preparations contain stains.

NOTE: Metal mortars and pestles should never be used when the drugs are likely to react with the metals.

Spatula
The spatula is a knifelike utensil with a rounded, flexible, smoothly ground blade, available in various sizes. The spatula is used to "work" powders, ointments, and creams in the process of levigation (the rubbing, grinding, or reduction to a fine powder with or without the addition of a liquid) and trituration. It is also used to transfer quantities of drugs from their containers to the prescription balance. Spatulas should not be used to pry open cans or as knives for opening boxes. Once the surface is scratched or the edges bent, the spatula is ruined, and it becomes useless for pharmacy work.

Graduates
Graduates are conical or cylindrical clear glass containers, graduated in specified quantities and used to measure liquids volumetrically. Measuring should always be done at eye level.