With added iron
Feedback pours scorn on the exam question concerning powdered iron in breakfast cereal
(3 June).
May I refer you to the excellent publication Classic Chemistry Demonstrations
published by the Education Division of the Royal Society of Chemistry, demonstration number 3,
“Extracting iron from breakfast cereal”.
Also, why is it difficult to believe that ingesting metallic iron may counter
anaemia? If you were to complete the word equation in part (c) of the exam
question you quote, you would realise that iron reacts with hydrochloric acid to
produce a soluble iron chloride salt which, presumably, could be absorbed into
the bloodstream and utilised in the production of haemoglobin.
Letter
My second-year science class tried out Colin’s experiment last year and, yes,
did find iron filings sticking to the magnet. Try it.
A matter of taste
The discovery that salt makes sugar taste sweeter
(13 May, p 19)
is not so novel. In South-East Asia, street vendors selling fresh pineapple pieces will
lace your purchase with soy sauce unless you ask them not to.
The effect of this rather non-intuitive topping is to mask the sourness of
any fruit that is not drippingly ripe. It’s the salt that does this, as you will
discover if you liberally sprinkle it over the unripe pineapple that is
generally offered in British shops. Try it鈥攜our friends will be
amazed.
Artefact
According to your correspondent J. Davies, hedgehog droppings are long and tapered
(3 June, p 53).
Davies suggests that the shape of the droppings may reflect the ancient grouping of
the hedgehogs and their unique defence mechanism.
I would have thought, however, that if you were defenceless and edible
looking, your droppings would be long and tapered, whereas if you were covered in prickly
spines, you could take as much time as you needed, resulting in, well, very artistic and carefully
constructed droppings?
Perhaps it was the (relatively) recent arrival of the Gypsies with their
novel hedgehog-in-clay recipe that really changed the toilet habits of
hedgehogs?
Jam on it
I think that the strange flavouring of the jam in Jammie Wagon Wheels is to
solve a technical viscosity problem
(Feedback, 27 May).
Raspberry jam does not have much pectin and is a difficult “set”. Plum jam is
rich in pectin and sets well, but raspberry is a more acceptable flavour. Hence
the combination.
Correction
In the letter from Adriaan Kortlandt
(6 May, p 52),
the name of Nobel Laureate and physicist Hendrick Lorentz was mistakenly
printed as Lorenz and wrongly given the first name of the Nobel Laureate
ethologist Konrad. Our apologies for any confusion this may have caused.
Rotten dams
Your article on rotting vegetation in dam reservoirs gives the unduly
simplistic impression that the observed greenhouse gas (GHG) emissions from a
few Brazilian dams means that all dams are bad
(3 June, p 4).
Contrary to your article, reservoirs in boreal areas and at least half the
Brazilian dams studied appear, on balance, to be more effective at avoiding GHG
emissions than the thermal alternative.
More importantly, your correspondent ignored the emphasis on GHG emissions
from natural habitats. Undeveloped Amazonian flood plains emit large quantities
of methane. So it is incorrect to conclude “a reservoir will produce more
methane than the river did before the dam was built”.
The workshop report of the World Commission on Dams, which incidentally
reflects the views of the participants, not those of the commission, emphasises
the scientific complexities involved with increasing power production while
reducing life cycle emissions from dams or other energy options.
Letter
Fred Pearce’s report will help alert the public and decision makers to reject
the dam industry’s claims that hydropower is a “carbon-free” electricity
source.
One major greenhouse-gas emitting reservoir that Pearce did not mention lies
behind the huge Tucuru铆 Dam in the Brazilian Amazon. Recent calculations
by Philip Fearnside of the National Research Institute of the Amazon indicates
that in 1990 this 2430-square-kilometre reservoir had as much impact on global
warming as all the fossil fuels burned by the 17-million-strong population of
S茫o Paulo. The emissions are roughly equivalent to those of a gas power
plant producing the same amount of energy as the 4000-megawatt
罢耻肠耻谤耻铆.
Fearnside’s latest estimate for Tucuru铆 emissions, which has not yet
been published, is more than twice an earlier estimate, mainly because he takes
account of recent research showing substantial methane emissions from dam
turbines and spillways.
The World Commission on Dams, which appears to seek to downplay the
significance of its own findings on reservoir emissions, stresses that natural
wetlands in the Amazon emit substantial amounts of methane, so flooding these
wetlands with reservoirs may not significantly increase emissions.
Fearnside, however, explains that little of the land flooded by
Tucuru铆 was wetland.
Soy story
Andy Coghlan highlights the issue of seed becoming contaminated with
genetically modified varieties
(27 May, p 4).
Sloppy practice by the seed companies seems to be behind this. The spacing of
GM and non-GM crops will have to be reviewed both here and abroad to supply
the non-GM seed that is so clearly in demand.
However, your piece confuses imports of seed for growing and those for food
and feed uses, such as soybeans. Soybeans are hardly grown in Britain, and the
491 000 tonnes of them that were imported from North America last year were for
processing, mainly for use in animal feeds. Since 50 to 60 per cent of the US
soybean crop was GM in 1999, a more accurate estimate of imports of GM soybeans
last year would have been 250 000 tonnes.
This is one of the secret ways GM crops get into the food chain. Like the
regulatory hole for seed purity in relation to GM, there are no regulations
covering the safety and use of GM ingredients in animal feeds. Human safety
tests cannot be simply extrapolated to farm animals because they may be eating
much larger quantities of the GM product over prolonged periods and have very
different physiologies from humans.
It's no joke
Your feature on the mechanisms of laughter suggests that humour is simply a luxury
(27 May, p 22).
This surely cannot be the case for something that forms such a large part of our social
interaction.
To find an evolutionary advantage for laughter, we should look at it as a
learning mechanism. What your article called “cognitive” laughter is, I suggest,
a way of exploring the boundaries of the rules for being a human.
In slapstick humour, we laugh as people fall over or get hit by custard pies.
It is bad to fall over, because you might get injured. And what about the clown
who turns round while carrying a ladder over his shoulder, hitting his colleague
on the back of the head? This is a real lesson to a young child. The laughter of
those around the child says “take note, this is inappropriate behaviour”.
More complex jokes carry out the same process. The “which side of a dog has
the most hair?” is a test of the understanding of language. We laugh because the
joke teller has deliberately misunderstood the normal way in which the words of
the joke are understood. In a “serious” situation, this deviation from normal
language could be harmful. You would not confuse “side” meaning “left/right”
with “inside/outside” in that job interview at a veterinary college.
If language is an important evolutionary development for humans, laughter at
the misuse of language helps reinforce the rules for the use of language. This
is all part of the play/learn process, but in a verbal context.
Look through the latest jokes you have been e-mailed. I suggest that every
one is about breaking the rules of being human. Remember that some of the rules
are ones we are aware of having learned (how to use a computer) and some not
(how we would normally talk about a hairy dog).
We enjoy laughter, just as we enjoy eating, sex, playing and
resting鈥攁ll very important activities for the survival of the species. If
enjoyment is not to be devalued, then it can only be used to reward important
activities. Laughter, surely, is no luxury.
Letter
Your article is spoilt by its anthropomorphic approach to the subject. Its
constant reference to the higher centres of the human brain shows a lack of
understanding that animals, too, have a well-developed sense of humour.
I have seen a mule deliberately play tricks on her human companion and then
flee with a gesture that was unmistakably laughter. I have witnessed that same
animal play tricks on her long-suffering aged donkey companion. I have seen that
donkey opportunistically repay her in kind. These are personal experiences, but
there are other examples on record.
Getting sloshed
Could not the effect of “slosh” in spacecraft fuel tanks
(27 May, p 32)
be minimised by the same effect used in the dreaded “wine box”, where the liquid is
in a flexible internal membrane?
The space between the outer and inner membrane of the tank would only need to
be pressurised to the same level as the spacecraft to achieve the effect.
Humps aplenty
Your correspondent John Burton states that “the one-humped camel is not known
in the wild”
(Letters, 27 May, p 53).
Not in its original homeland perhaps, but one-humped camels are found wild in central
Australia. Descended from domesticated camels that were released or escaped, they
apparently thrive.