The psychoactive agent in alcoholic beverages is ethyl alcohol
or ethanol (C2H5OH) – It completely clear, odourless,
tasteless and water soluble. Various other chemicals in the
beverage are responsible for the taste and odour we commonly
associate with liquor!
The intoxicating potency of any alcoholic beverage (the primary
psychoactive agent in which is ethanol) is measured in terms of
ethyl alcohol content which is usually expressed in terms of volume
for volume or mass per volume – Given that 1L of alcohol does
not have the same mass as that of the equivalent volume of water,
concentrations of ethanol expressed in g/L must be multiplied by
the factor 20/21 to yield concentrations in g/Kg. This is important
as most lab reports will state blood ethanol concentrations in
g/100mL. Always be conscious of the units you are working with!
Ethanol is readily water soluble and passes easily through the
cell membranes of the gastrointestinal tract. Ethanol taken by
mouth is therefore rapidly and almost completely absorbed –
Some absorption takes place in the stomach with the majority
occurring in the small intestine (+-80%). On an empty stomach a
large drink will be completely absorbed within an hour, and in the
presence of food this time period may extend to over 2 hours. A
number of factors influence the rate of ethanol absorption from the
gut:
>>> Gastric emptying time is
inversely proportional to absorption time and is prolonged in the
presence of certain foodstuffs – Fatty foods and proteins
delay empting the most while carbohydrates do so the least. This is
the major factor influencing rate of absorption.
>>> Alcoholics, due to chronic mucosal irritation of
the stomach, tend to absorb alcohol more quickly from their
stomachs than do non-habitual drinkers.
>>> The concentration of ethanol in the beverage also
influences the rate of absorption – High concentrations
(excess of 20%) are absorbed more slowly owing to acute gastritis
than beverages of lower concentrations.
Once absorbed, ethanol is distributed by the blood to all the
tissues of the body (the concentration in the various tissues in
proportional to the water content of that tissue). Fat, which is a
relatively dry tissue will offer less space for alcohol
distribution than would muscle, which contains much more water.
As many can testify, ethanol can do funny things to the mind.
Effects are due to depressant action on the ganglion cells of the
central nervous system and one of the reasons that the substance is
popular is that depressant effects are selective at moderate doses
– at these doses only higher centres of function are
affected, while lower centres are spared. Thus at these moderate
doses vegetative functions such as breathing and blood circulation
are little affected, but our overly stressed minds are depressed
with resultant euphoria, dulling of intellect and diminution of
ability to restrain behaviour.
Unfortunately our higher cognitive abilities are essential in
the making rational decisions and the safe operation motor vehicles
– The law has thus stated (Act No. 93 of 1996, Chapter 11,
Section 65, Sub-section 2): No person shall on a public road drive
a vehicle; or occupy the driver’s seat of a motor vehicle,
the engine of which is running, while the concentration of alcohol
in any specimen of blood taken from any part of his or her body is
not less than 0.05 grams per 100 millilitres.
A very interesting phenomenon, regarding the effects of ethanol
at various concentrations, was described by Mellanby and bears his
name – When the ethanol concentration to the brain is on the
rise and is found to be at a level X a patient exhibits greater
signs of intoxication than the same patient with the same
concentration of ethanol but which is on the decline – I.E.
If your ethanol level is rising, as opposed to falling, you will
experience greater effects of ethanol for a given blood ethanol
concentration… Just interesting…
Another smart gentleman by the name of Winmark described a way
of calculating the quantity of alcohol one needs to consume in
order to achieve a certain blood-ethanol concentration. Difficulty
in calculation arises due to the fact that the various tissues of
the body have differing water content and thus concentration is
dependant not only on body size, but also body constituents.
Widmark defined a variable known as the “r” factor
– this is the ratio of blood:body ethanol concentration. The
value of r is chosen according to body physique (0.495 in obese
individuals, 0.765 in lean muscular individuals and for those with
average physique, 0.68)
Widmark’s formula: A = p x c x r where A is amount of
ethanol consumed in grams; p is the weight of the subject in
kilograms; c is the blood ethanol concentration in g/Kg; and r is
the “r” factor described above. This formula is not
intended for calculation of the amount of alcohol consumed in a
sitting as it does not take into account metabolism during
consumption.
As mentioned before, ethanol exhibits zero order kinetics in the
human body – this means that regardless of the concentration
of ethanol in the body, the body is able to metabolize the ethanol
to acetaldehyde at a constant rate until there is no ethanol
remaining in the body. Very few substances behave this way. The
vast majority of ethanol (90%) is metabolized in the liver by
anaerobic oxidation by the enzyme alcohol dehydrogenase to
acetaldehyde (Antabuse, a drug used to curb alcohol addiction,
inhibits this enzyme resulting in severe illness on alcohol
consumption; This enzyme is less effective in people of Asian
origin which also explains the low prevalence of alcoholism among
this group). The remaining ethanol is excreted unchanged in the
urine and breath. For the vast majority of people clearance of
ethanol is between 6-8g per hour. Clearance may be more rapid in
habitual drinkers owing to activation of the Cytochrome P450 enzyme
system in the liver (increase in rate of metabolism by ~15%)
Your task as a responsible geocacher is to help out your
friend… After having been unable to find Water ~ Testing
your chemistry, another cache on Blouberg beach, he assumed a seat
at a restaurant here at Eden on the Bay and decided to order a
drink (perhaps hoping that the solution would come to him). He is
rather chubby, of average height with BMI of 32 and a mass of 99Kg.
He had eaten no food for some hours and decided to order a Jam Jar
with everything in it (23.6g of ethanol). At the same time some of
his high school buddies notice him sitting in the corner looking
quite dejected and they buy him 3 vodka shots (25.3g of ethanol)
– Not wanting to offend his friends he downs the shots and
sits down again to finish his Jam Jar. He finishes the drink in
little time and soon begins to feel quite relaxed… You
arrive and he tells you of his failed attempt at Water ~ Testing
you chemistry. You have solved this particular cache and advise
that he remember that diffusion rate is inversely proportional to
the root of the molecular mass of the gas and that he must simply
determine relatively how much faster the lighter gas diffuses
– divide the root of the molecular mass of the one gas by the
same for the other gas. The resultant rate ratio will equate to the
proportion of the gas that can be extracted for every pass through
the diffuser. After each pass there is now less of the lighter gas
and the amount extracted decreases slightly after each pass. An
arithmetic progression… ;) Anyway - he stares blankly - It
comes time to leave and your friend, who only ever drinks once in a
blue moon, stumbles and then sits back down… He asks you
whether you think he is over the legal limit, and if so, how much
longer he should sit at the restaurant before he is below the legal
limit…
Assume that all the ethanol was absorbed within 30min during
which time an insignificant amount had been metabolised. Assume
also that your friend will metabolize the ethanol as would an
average adult from the moment that all the ethanol has been
absorbed – Err on the side of safety and calculate based on
the slowest average rate of metabolism for an average person. You
need to advise your friend as to what his blood ethanol
concentration is likely to be right now, at 30min post starting to
drink, and for how long he should sit it out before hitting the
road…
(Calculate his blood ethanol concentration in terms of mg/L
rounded off to the nearest mg [this yields ABCD]; Calculate the
amount of time he he should wait before driving rounded to the
nearest minute [this yields EFG])
The cache will not be found at the listed coordinates and the
puzzle will lead you to only further down the rabbit hole…
If you get stuck thinking in reverse may be enlightening! ;)
***NB!! At the coordinates calculated below you will find
nothing that needs removal or extraction… Just use your
senses! No muscle required. PLEASE DO NOT BREAK OFF OR PULL
ANYTHING WHICH COULD BE PART OF THE PUZZLE!***
The cache has a theme ~ which will be made clear after decoding
the intermediate... But bring some foreign coins if you have any ;)
An immense amount of effort has gone into this so please let's keep
the cache loaded!
The final cache is EXTREMELY VULNERABLE and is located in a HIGH
MUGGLE ZONE! Please attempt this cache at NIGHT ONLY. Retrieval of
the final will attract much attention. You will need time to
appreciate the cache so return when the area is deserted! My advice
is to go with a friend, use very dim headlamps (cover with tape),
and hit it after midnight!
S 33 47.(G-A)(F)(F+A+E)
For the intermediate stage: ***Use stealth***
For the final: ***NIGHT TIME ONLY*** (Or driving rain - the kind
where all sane people are indoors!)
E 18 27.(D-F)(B+F+C)(D+A)
