Weigh boats

[WK]

Standard procedure to use these to transfer powders to volumetric flasks I know.
I don't like them since there is ample opportunity for powder to float out when tipping up and tapping out (even though you have reweighed and calculated the difference).
Can anyone point me to a paper on this?
I propose to weigh (mgs) into a 50ml beaker and dissolve in solvent in the beaker then transfer to the volumetric with plenty of washings - taking care not to lose standard down the outside of the beaker spout.
I suppose there is less chance of losing powder if you spoon it near to the spout end?
WK

[David Blais]

WK,

Can't point you to a paper, but if you don't like the weigh boats, may I recommend glass (or plastic) weighing funnels? Fisher (and probably VWR) carries them, I use them and highly recommend them. They come in different sizes for your needs and the necks fit perfectly into the 50mL volumetric flasks you use. Fisher part#s are 14-353B (15mm diameter x 40mm length), 14-353D (25mm diameter x 55mm length), 14-353F (assortment pack of 5, one each of 5 different dimensions).

Good luck.

-Dave

[WK]

Thanks David,
These are what I am using at the moment. Its catch22. If I want a 50mg/L solution, I can make a 500mg/L with a 100mL flask (weighing into the flask) and then add error by diluting.
Or I can use a weighing funnel for 50mg into 1000mL and run the risk of losing some in transit and washing in.
WK

[aldij]

i allways weight my standards direct in the flask. is this a very bad thing?

[David Blais]

Aldij,

Weighing directly into a flask is not a bad thing. With some methods the flask needed may be very large and as such, will not physically fit on a balance. Or the weight of the flask may simply be greater than the maximum limit of the balance.