A torsion prescription balance has a sensitivity requirement of 6 milligrams. Explain how you would weigh 4 milligrams of atropine sulfate with an accuracy of 5%, using lactose as the diluent.
To weigh 4 milligrams of atropine sulfate with an accuracy of 5% using lactose as the diluent, the following steps can be followed:
1. Begin by calculating the maximum allowable error or deviation in the weight. Since the sensitivity requirement of the torsion prescription balance is 6 milligrams, the maximum allowable error would be 6 milligrams * 5% = 0.3 milligrams.
2. Determine the desired amount of atropine sulfate to be weighed. In this case, it is 4 milligrams.
3. Add the maximum allowable error to the desired weight to obtain the upper limit of the acceptable weight range. 4 milligrams + 0.3 milligrams = 4.3 milligrams.
4. Subtract the maximum allowable error from the desired weight to obtain the lower limit of the acceptable weight range. 4 milligrams - 0.3 milligrams = 3.7 milligrams.
5. Prepare a mixture of lactose and atropine sulfate in a ratio that falls within the acceptable weight range. For example, a 50:50 ratio can be chosen.
- Weigh out 2 milligrams of atropine sulfate.
- Weigh out 2 milligrams of lactose.
6. Mix the weighed amounts of atropine sulfate and lactose thoroughly to ensure a homogeneous mixture.
By following these steps, 4 milligrams of atropine sulfate can be accurately weighed with an accuracy of 5% using lactose as the diluent. The torsion prescription balance should be able to weigh within the acceptable weight range limits, taking into consideration the sensitivity requirement of 6 milligrams.