You know that in every dynamic 1st order reaction (a reaction with a fixed rate of promotion) we can say that:

N=N0.e**(-kt)

where N is the amount of sample remained after the time t

THEN

N/N0=e**(-kt) and

ln (N/N0)= -kt and

t= (-ln(N/N0))/k

half life is when N/N0=1/2.

THEN:

t1/2=(-ln(1/2))/k = ln2/k.

this is simply equal to:

t1/2=0.693/k.

This formula has been discovered by Ernest Rutherford in 1900.

Good Luck:)

Thank you, and you are welcome:)

Thank you very much. It really helped.

OK. You are welcome:)

Where do you get e** from and what is it? Where do you get N=N0.e**(-kt) from?

Dear Dragan,

Thank you for your post.

The expression "e**" actually means the number "e" (2.718) in the power of (-kt).

This equation has been discovered by Ernst Rutherford in 1900.

Good Luck

Thanks, it is probably great, but, sorry, it does not explain what is "e**". The irrational number with two stars? OK, but why the two stars? An then you say "in the power of (-kt)". Well, what is this then? And then how the two stars disappeared? Sorry, it is hard to understand.

Thanks very much for your effort.

I believe the "computer notation (e.g. in excel)" would be N = N0 * e^(-kt). Does this clarify the equation for you?

Sorry, no. May be you did not get my “message”. I suggest that we all open a textbook and look it up, and then discuss. Believe me it is hard to find a textbook on pharmacokinetics which does not fully develop the equation of half-time. Internet is also full of various forms of the proofs of radioactive decay, even fully explained Rutherford’s calculations could be found. Even Prism (Graphpad) has built in program for calculation. And then the question has been asked at various Internet forums number of times and answered correctly… So why bit about the bush?

Dear Dragan,

I got your message.

OK. You are right. But some people prefer to use media or other information sources even for the science.

You know. Sometimes there is a question, and it is better to be answered in that environment and not to be referred.

Such a way help the expansion of interrelationships among scientists.

This is of value and may not be time wasting, although perspectives are different on such issues person-by-person.

Thank you again for your message.

Good Luck

Dear Younes,

You appear to be right too. Yes, your point is that we should keep discussing and my point is to try to be more transparent, to use more common language and be more simple. All the best.

Thank you Younes