Most people that have never worked with small quantities have never seen 1
ppm of anything. They can only guess at the actual quantity that 1 ppm
represents.
With some materials, you will never see 1 ppm or even 5 or 10.
Others you can see, vividly.
That is what I want to show you, how to make 1 ppm, or maybe 3, and
actually see it.
This has little to do with the units discussion or with CS, but it will
show you how small 1 ppm or 3 ppm actually is.
Recap of units and the ratio of mg to grains
1 pound = 453.5924 grams = 453 592.37 milligrams
1 pound = 7 000 grains
1 grain = 64.7989 mg ( usually considered and used as 65 )
The grain is the unit we will be using. or rather the .1 grain
.1 grain = 6.4708 mg ( usually used as 6.5 mg per .1 grain )
Typically, half this amount, 1/2 of .1 grain = .05 grain
( is the smallest resolution the eye can manage )
.05 grain is equal to 3.25 mg or 3.25 ppm weight.
This is only true when using the one liter standard.
1 ppm of a 500 gallon tank is different, as are other volumes and weights.
The lead mass can only be compared to the 1 ppm in the one liter volume.
Easy Experiment
Use a small piece of paper. Approx 1.5 inches by 2.0 inches
With a good grain scale, this can be weighed. It could be also be
weighed with a mg scale but few have those other than labs.
Now......... Write you name on the paper using a common lead pencil.
A # 2 wooden pencil would be best. Point should be medium sharp, not
dull or not really sharp as just out of a good quality pencil sharpener.
Of course you can use a mechanical pencil with small lead or a carpenter
pencil, but the value of the weight will be different.
You can now weigh the amount of lead that is required to write your name.
If it is a double or triple name, you might have 1 ppm of lead ( or
equivalent weight ) in one part of your name. In 3 names, maybe 3 to 4 ppm
of weight.
If you have a long complex name, the total lead may be as high as 4 or 5 mg.
Again, the lead hardness and width can effect this. This is about as close
as you can get to see 1 ppm, 3 ppm or maybe 5 ppm.
After doing it a few times, you would become more skilled at weighing your
name. Good balance or beam scales can do this. A digital grain or mg
scale should do even better, but only if it is good quality and high dollar.
The cheap ones are worthless for this and most other tasks that require
small measurements under 20 to 50 mg.
I have done this a number of times over the years. The result can be
relatively consistent.
Eliminate any air movement, fans, air conditioners, ect. They can move
and disturb the beam dampening.
For comparison, the grain is about 65 times larger than the mg.
You might have fun weighing fleas, ticks, house flies, and chiggers.
If you find out how many ppm they are, please tell me.
Wayne
