Hi again,
I told Harry about god's suggestion, he looked for a detailed explaination and here is what he found :
Most drug stores in the late 19th and early 20th century prepared tablets using tablet triturate molds. The tablets were also called molded tablets and were made from a paste-like mixture of the drug.
Tablet triturate molds are made of metal. There are two plates, the cavity plate is the plate that has only holes and the peg plate that has pegs. The mold will indicate the capacity of one cavity in the cavity plate but that indication is only an approximation. Typical die plate cavity sizes are 60 mg and 100 mg.
The volume of the cavities always remains constant, but the weight of the tablet made will depend nature of the material. Different bases will have different densities and so the cavity capacity must be determined for each base, e.g., the mold must be calibrated. (This is the same reason why all molds must be calibrated for each base.)
Calibration of the mold:
1. Tablets that contain only the powder base are made first. The tablets produced are weighed as a batch and the average weight per tablet for that base is calculated.
2. The average weight per tablet of the active drug is determined. Generally, just a few cavities are used in this determination. Tablets containing only the active drug are made and the average weight per tablet for the drug is calculated.
3. The quantity of drug that will be required in the prescription per tablet is divided by the average weight per tablet of the active drug. This will give a percentage of the cavity volume that will be occupied by the active drug
4. Subtracting the percentage in step 3 from 100% will give the percentage of the cavity volume that will be occupied by the tablet base.
5. The percentage of active drug in the cavity volume and the percentage of base in the cavity volume are used to calculate the appropriate amounts of base and drug to weigh. For example, if the mold contains 50 cavities and each will hold approximately 100 mg, then 5000 mg of mixture will be needed to fill the mold. The amount of base and drug to weigh can be determined by multiplying 5000 mg by the two different percentages determined in the preceding steps.
6. It is prudent to prepare a slight excess of powder mixture (5 - 10%). This will allow for any variance in the approximate and actually capacity of the mold, and will also allow for powder loss during the compounding procedure.
To compound the molded tablets, prepare the powder mixture by proper techniques and sift the mixture through a 80-100 mesh sieve. Then moisten the powder mixture until the mass has the consistency of "Play Dough." Press the mass into the cavities of the cavity plate. Have the plate on an ointment tile or glass plate. A hard rubber spatula should be used to press the material into the cavities; stainless steel spatulas will scratch the surface of the metal plate. Sufficient pressure should be applied to tightly pack each cavity with base.
It is important to insure that all cavities are equally filled especially the marginal cavities. Both sides of the cavity plate should be inspected to made sure that all of the space in each cavity is filled. When the cavity plate is loaded, the plate is placed on the peg plate so that the pegs are aligned with the holes. The cavity plate is then carefully pressed onto the peg plate. As the cavity plate falls, the tablets are pushed out of the cavity plate onto the tops of the pegs. The tablets are left on the pegs until they dry.
So I guess it will do the trick...
