hot plate stirrer experiments, when the need to be formulated with the direct preparation method specified concentration standard solution, often with specified weight weighing method to weigh standard compounds. This method can only be used for Weigh difficult hygroscopic effect exclude the various components in the air, the nature and stability of the powder-like substance. Does not apply to the bulk material weighing.
The specific method of operation is as follows:
① First tuned balance of zero, with the metallic tweezers, clean, dry container (ceramic crucible, furrow small surface of the dish) on the left said the weight of the disk on the right disk to reach a balance.
② right disk increase with the alleged the sample amount equal weight, then gradually adding the sample with a small horn spoon, half-opened the balance test weight. Until the added when sample only a thin small weight, you can open the balance, extremely careful in his left hand holding containing samples of horn spoon toward the central part of the container about 2 ~ 3cm above, with the left thumb, middle finger and palm Hold the the horn spoon handle, to allow the sample in the spoon shaking into the container at a very slow speed.
③ At this time, the eyes should not only pay attention to the horn spoon, as well as watching differential signage projection screen, to be differential the signs just needed to move the scale immediately stop shaking into the sample. Note that the right hand not to leave the lift pivot.
This step must be very careful, if inadvertently pay more samples, only to shut down the lift pivot with horn spoon remove the excess sample and repeat the operation until the desirable date.
hot plate stirrer operator should pay attention to:
① sample or remove the horn spoon, the sample must not be lost in the pan. The open balance pipetting, avoid adding too many samples, otherwise it would balance a sudden loss of balance;
The ② said good samples must be quantitatively transferred to the receiver of the treated samples.
(2) decreasing (subtractive) weighing method
That is said to take samples of the amount is determined by the difference between the two weights. So that the results are accurate weighing, but inconvenience Weigh specified weight.
The specific method of operation is as follows:
① First tuned balance of zero, with the metallic tweezers, clean, dry container (ceramic crucible, furrow small surface of the dish) on the left said the weight of the disk on the right disk to reach a balance.
② right disk increase with the alleged the sample amount equal weight, then gradually adding the sample with a small horn spoon, half-opened the balance test weight. Until the added when sample only a thin small weight, you can open the balance, extremely careful in his left hand holding containing samples of horn spoon toward the central part of the container about 2 ~ 3cm above, with the left thumb, middle finger and palm Hold the the horn spoon handle, to allow the sample in the spoon shaking into the container at a very slow speed.
③ At this time, the eyes should not only pay attention to the horn spoon, as well as watching differential signage projection screen, to be differential the signs just needed to move the scale immediately stop shaking into the sample. Note that the right hand not to leave the lift pivot.
This step must be very careful, if inadvertently pay more samples, only to shut down the lift pivot with horn spoon remove the excess sample and repeat the operation until the desirable date.
hot plate stirrer operator should pay attention to:
① sample or remove the horn spoon, the sample must not be lost in the pan. The open balance pipetting, avoid adding too many samples, otherwise it would balance a sudden loss of balance;
The ② said good samples must be quantitatively transferred to the receiver of the treated samples.
(2) decreasing (subtractive) weighing method
That is said to take samples of the amount is determined by the difference between the two weights. So that the results are accurate weighing, but inconvenience Weigh specified weight.
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