Can you check these calculations please?

[Slightly Blue Dalmation]

have fun measuring out 5mg of what he wants need to have a conc in bottle to get a value in mls that can measure

[tHEcONCH]

Bottle size is irrelivant - its still 4%, i.e, 4 parts in every hundred regardless of how many parts are in the bottle. 4% in a 250ml bottle is still the same concentration as 4% in a 1 litre bottle. Maybe we need him to clarify what he means by 'concentration is 4%' before we can go much further.

[Slightly Blue Dalmation]

4g/l is 4000mg/l and where did the 200000 come from? it should stay in L to keep units the same

[Slightly Blue Dalmation]

yeah but it still doesnt say how much of the stuff he wants is in the bottle whatever size it is

[Caryl]

Husband Grant is agreeing with everything tHE cONCH said. It needs 500mg of the meds but since it isn't stated whether the 4% is volume or weight, we don't know how to relate the 500mg to whatever's in the bottle. Grant came up with 500mg of meds but since we don't know what the 4% relates to we can't say how much to use.

[purplecatfish]

Maths Question:

The medication concentration is 4%,

And a final concentration of 0.1 mg/L is needed,

The Tank is 200L,

Is the dose A) 0.5ml or B) 5ml

Its a maths question and the answer is either A or B. The problem is related to the order of magnitude.

The amounts and type of medication are irrevelant but because you're all interested it's Malachite Green and I have 100ml so there's enough to treat the tank several times.

One the beauties of the metric system is that because 1000g = 1000ml of water then %, mg (weight) and ml (volume) become interchangeable.

Thus a 4% solution contains 4g in 100ml

As 200 / 4 = 50 then the last thing to work out is where the decimel point sits.

A or B?

[Dixon1990]

i say b. but im no expertso wait for other answers too.

[Adrienne]

4% is 4gr per 100mls w/v

you require .02grms (20mg) for the tank

which is roughly a dose of .05ml or one drop

This comes from my husband who is head of science and a chemistry and maths teacher.

[Slightly Blue Dalmation]

thanks caryl that summed up what my poor england was trying to say

[Slightly Blue Dalmation]

yup .04/.05/1dropish

[Adrienne]

my husband also said ' why does it matter'

'its only fish'

and

'tip the whole bottle in'

:evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil: :evil:

[tHEcONCH]

:lol:

[Slightly Blue Dalmation]

not a fish guy then haha

[alanmin4304]

The 200000 comes from the other side of the brain and gave the same answer (after some practice) as the head of the science dept who don't like fish.

[alanmin4304]

I worked it out in mls not litres.

[cadeusus]

4% is usually w/v...i.e 4g/100mL

therefore 100mL contains 4000mg

therefore 1 ml contains 40mg

if he wants 0.1 mg/L in 200L that is 200 x 0.1 = 20mg

therefore 0.5mL

The only thing to check is if 4% is 4% w/v

[tHEcONCH]

Yep.

[Dixon1990]

My Malachite Green bottle says 2% w/v

[Adrienne]

stronger stuff up here obviously more bugs!!!!!

only likes his discus

and

watching me clean the tank for him :evil:

[tHEcONCH]

stronger stuff up here obviously more bugs!!!!!

only likes his discus

and

watching me clean the tank for him :evil:

I think I like this guy already! Do you wear a french maid outfit when you are cleaning the tank?

[Adrienne]

:lol: :evil: :lol: :oops:

[Warren]

I get 500mg or 0.5g

200L @ 0.1mg/L = 20mg

20mg / 0.04 (4%) = 500mg of medication

As the solution is 96% water, the solids represent a fairly low part of the weight. Therefore the error using 0.5mls (500mg) of the solution will be small enough to ignore.