Penta Water
Penta Water (sometimes called AquaRxTM Water) is a commercially sold brand of bottled water that is claimed by its manufacturer to be structurally different from 'normal' water. It is advertised as the 'ultimate bottled water' on Penta's official website. It is manufactured and distributed by sister companies Bio Hydration Research Lab and AquaPhotonics. Penta's name derives from its association with five-molecule clusters of water.
In particular, Bio Hydration Research Labs states that their 'Penta process' of subjecting water to high energy sound waves, creating sonoluminescence, reduces the average size of the water clusters present in liquid water. This supposedly makes it easier for water molecules to pass through cell membranes. It is further claimed that water so treated improves the 'survivability' of cells. In 2003, Penta became the best selling bottled water in American health food stores.
The various claims made by Penta are classed as pseudoscience by scientists , as they have never been scientifically established. Penta has commissioned studies which appear to validate a few of their claims, but none of these studies was published in mainstream peer-reviewed scientific literature. These studies also suffer from major experimental design flaws.
Penta is a registered trademark of Aquaphotonics, Inc.  In physical chemistry, the commonly used (non-trademarked) term for a cluster of five water molecules is the water pentamer.

# Claims made by Penta
This is a list of past specific claims for Penta found on websites once maintained and owned by Penta/Bio Hydration Research Labs/Aquaphotonics and targeting the U.S. market. Current claims are solely for "higher purity".
- Penta Water contains water clusters of fewer molecules than normal water. 
- Penta Water has a 30% reduction in cluster size. *
- Penta Water enters cells 14% faster than normal water. *
- Cells cultured in Penta Water survive 266% longer than in normal water. 
- Cells cultured in Penta Water have a 3 decrease in acidity compared to cells cultured in distilled water.
- Athletic performance measurably improves after consumption of Penta Water. 
- Penta Water has a higher boiling point than normal water and this is not due to dissolved impurities. *
- Penta is easier to drink than normal water. 
- Penta aids in weight loss. *
- Penta is the purest bottled water on the market.
- In vitro, Penta dissolves kidney stones faster than lab water.
- DNA mutation is 271% greater in distilled water than in Penta Water.*
- Penta is 16.7 faster water. *
- "..healthier skin, hair, and joints; stronger immune system; faster recovery from surgery or physical activity; and reduced hypertension and cholesterol." Bill Holloway, Penta CEO.
- Increased energy and mental alertness.
- Helps houseplants grow. *
- Penta has helped clear up skin problems. *
- Protein crystals grown in Penta have a different structure.
- Featured testimonial on Penta website claims Penta can help with fibromyalgia, lupus, arthritis, or chronic fatigue syndrome.
- Featured testimonial on Penta website claims Penta can help with diabetes.
- Penta acts like an energy drink. *
- It has helped to reduce the side effects of chemotherapy treatment for cancer. *
- Adding Penta to Pap smear test samples increases the accuracy of cervical cancer screenings.
- Scavenges free radicals.
- Enhances absorption of moisturiser cream onto skin. *
All of the entries marked by an asterisk (*) were found on the UK Penta web pages which have now been taken offline due to Penta being forced to cease trading in Britain. 
Many of these specific claims are criticized on a skeptic's website . The claims have also been discussed in a commentary by James Randi  and in Ben Goldacre's Bad Science column in The Guardian (for which, it is claimed, he received hate mail).

# Reliability of claims
The Penta Water website claims  that a paper has appeared in a peer-reviewed journal validating one of their claims that Penta Water contains smaller clusters (30% smaller) than 'normal' bulk liquid water: Study of cluster molecular structures in various types of liquid water by using spontaneous Raman Spectroscopy, A. F. Bunkin, A. A. Nyrmatov, and S. M. Pershin, Physics of Vibrations, Volume 10 Number 2, 2002.  Physics of Vibrations changed its name to Physics of Wave Phenomena in 2003 and is a Russian physics journal published by Allerton Press . The paper in question discusses differences in the Raman Spectra between Penta water and normal lab water. There is no discussion of any possible health benefits.
At the time of writing (March 2005), there are no peer-reviewed papers in the scientific literature showing any health benefits of Penta water.  In fact, the Penta Water web site makes several claims from studies that "are pending publication".  Other such claims, from other "pending publications" have disappeared from their site.
The claim that smaller water clusters are present in Penta Water appears to mean that there are fewer molecules in each cluster, not that the actual physical size of a particular molecule is smaller. No explanation has been given for a proposed mechanism that creates these smaller clusters. Apart from the aforementioned interpretation of Raman Spectra results, there is no published evidence showing a reduction in the average number of monomers per cluster. In any case, claims for smaller clusters seem to be irrelevant to Penta's claim for 'better hydration', because water molecules only enter through aquaporin cell-membrane channels one at a time. This point was made by Oxford University professor Robert Williams in an article by Mark Henderson in The Times on 7th February 2004)
There has been no replication of these results or further evidence published in peer-reviewed scientific journals to support the claims of Penta/Bio Hydration Research Labs. Also, there is no known mechanism by which normal liquid water can be 'restructured'. Penta Water appears therefore to be pseudoscience.
If Penta's claims were found to be true, then noted skeptic James Randi has stated  that they would be  eligible for the Randi Prize of one million dollars for "anyone who is able to show evidence of any paranormal, supernatural, or occult power or event under test conditions agreed to by both parties". In July 2001, Penta agreed to submit to the Randi Prize, but later withdrew.  In April 2005, Mark Fairhead, director of Penta UK wrote that they were considering re-applying.
In addition to the Randi Prize, published evidence in peer reviewed mainstream scientific journals would make it likely that Penta would win the Nobel Prize for being able to demonstrate the restructuring of water and its improved health benefits.
An oft-used criticism of skeptics' literature such as Randi's website is that the skeptics are apparently dismissing a subject without personally carrying out scientific tests to see if the claims are true. However, the onus of proof is generally agreed to be upon the people or company making extraordinary claims and not the skeptics to try and duplicate every experiment. In general, skeptics such as Randi tend to point out where the claims disagree with well-known mainstream scientific principles and this does not by itself require any further testing on the part of the skeptic. In 2001 , the James Randi Educational Foundation offered to arrange for independent tests of Penta's claims with protocols to be agreed upon by the foundation and Penta. It is a matter of record that Penta have yet to accept the challenge.

# Mainstream science
It is important to note that the study of water clusters is real science. There is much spectroscopic evidence to show beyond the doubt of most physical chemists that water clusters exist under appropriate (gas-phase) conditions (see for example , ). Furthermore, there are many scientific papers published in major peer-reviewed journals, hypothesizing that bulk-liquid water can be thought of as conglomerates of macroscopic numbers of 'flickering' water clusters. However, there is not evidence yet of 'restructuring' on time-scales greater than tiny fractions of a second.
On the Penta Water links page  was included a link to a Cambridge University science group under the heading of "partnerships". In fact, this is false and the Cambridge science group has no association with Penta . There was also a similar link to Johns Hopkins University. Again, there is no evidence of a partnership between Penta and Johns Hopkins. (Note, as of March 23rd 2005 these links have been removed from their website, though it is still possible to view an archived copy of the links page.)  Up until Penta UK ceased trading, the now offline British Penta webpages  continued to link to a Cambridge water-cluster science page even though the page in question carries the clear and prominent disclaimer:
"PLEASE NOTE THAT LINKS FROM ANY COMMERCIAL ORGANISATIONS TO THIS SITE ARE ENTIRELY UNAUTHORISED AND UNWELCOME. THE MAINTAINERS OF THIS SITE HAVE NO CONNECTIONS WITH ANY SUCH COMPANIES OR THEIR PRODUCTS." 
Penta sister company AquaPhotonics claimed in a May 2005 Press release that Dr. Nikolai Tankovich, CEO of AquaPhotonics, had "joined the Scientific Advisory Board of Procter & Gamble". A reader of the James Randi webpage attempted to verify the accuracy of the press release with Procter & Gamble. A Procter & Gamble spokesperson replied:
"We are unaware of any advisory board Dr. Nikolai Tankovich is on with P&G" 
A few days later the press release was removed by AquaPhotonics from their news page. .
Penta has provided 15,000 in research funding to the British Brunel University in 2003 for a research study The ergogenic effects of Penta Water . Dr. Andy Sparks and Prof. Don MacLaren  from the Research Institute for Sport and Exercise Sciences in Liverpool John Moores University have also carried out research for Penta. (Their unpublished paper, Simulated soccer study is available from the AquaPhotonics website. )

# Response to criticism
In response to critical articles written by the British Guardian journalist, Ben Goldacre, in his Bad Science column, a Penta employee sent Goldacre the text message:
An apology, on behalf of Penta, from publicist Max Clifford followed. Goldacre contacted the British police in response to the threat.
In correspondence with James Randi , Penta CEO Bill Holloway wrote the following in response to Randi's request for Penta to follow their agreed upon protocol for application of the Randi Prize
The (now defunct) official British Penta website  had a page devoted to critical articles in the press in which they nominated newspapers and other news organizations for their 'Dunce Awards'. On this page, they respond to criticism with the following:
On this page Penta also states
At the time of writing (2005) these studies have not been published in peer reviewed journals, though the British Penta website did post quotes from researchers in two British sports research groups indicating that the studies were successful at demonstrating a performance improvement for athletes using Penta .  Details of these studies were scheduled to appear at the end of February 2005, but as of June 2006, they still have yet to appear.

# No longer sold in the United Kingdom
In March 2005 the British Advertising Standards Authority (ASA) ruled  on the accuracy of a Penta Water leaflet.  The complaint was upheld.  Among their findings the ASA wrote that
As a result of these findings, the ASA ruled that
The ASA is a regulatory authority set up as an independent body by the British advertising industry.  It does not have any statutory power, but it is usually able to enforce correct observance of advertising codes in Britain.
Penta has now been forced to cease trading in the United Kingdom.  It was reported in a commentary by James Randi that
The British Penta distributors have also apparently closed their Team Penta website, though they have left the message that
The Guardian's Bad Science column has also covered this event .

# Criticism of specific claims

## Boiling point
It is often mentioned that Penta has a higher boiling point than liquid water.  This claim appears to be based on a research report paid for by Penta on Measurements of the Boiling Temperature of Penta  Water.  In the study, which was not double blinded, the researchers found a 0.043 C increase in the boiling temperature of the Penta Water samples (relative to deionized water) and wrote
In this study, neither water was found to have exactly the expected boiling point of 100 C, which the researchers attributed to a probable error in the calibration of the thermometer.  Thus, the experiment was only able to measure the relative boiling points of the two waters.
The study was further discussed in an article in The Guardian Bad Science column .  One specific criticism of the experiment was that the quoted boiling temperature of the Penta sample appeared - contrary to thermodynamics -  to be greater than that of the water jacket heating it. Another was that the thermometer resolution was very likely insufficient to resolve the claimed 0.043 C temperature difference, but this point has been disputed. According to its makers , the Hart 1504 used has an accuracy of 0.003 C (at 0-25 C); the accuracy of 0.02 C. quoted by The Guardian may refer to the Hart 1502 or may be using the charted accuracy at 100C as listed on the chart here.
Note that similar claims of a raised boiling point have also been made for the now discredited polywater, which was investigated in the 1960s and was also proposed to be a new structure of water.  In the case of polywater, the elevated boiling point was eventually shown to be a result of dissolved impurities.

## Structure
The consensus in mainstream science (arrived at through numerous experiments and accumulated knowledge) is that water does not have a structural memory of the sort claimed by Penta or in homeopathy.  Even if smaller-than-average clusters are being formed by sound waves in the so-called "Penta-process", these structures would almost instantly disappear once the waves are stopped .
It is worth noting that the picture of five water molecules on every Penta Water bottle label does not represent a low-energy structure of the water pentamer since none of the waters are forming hydrogen bonds.  If molecules were placed in this geometry they would quickly repel each-other (whilst quickly reorienting) due to the mutual electrostatic repulsion of the negatively charged oxygens.  However this structure might occur around a positively charged ion such as Na+.  The accepted  lowest energy global minimum structure for five water molecules is shown in the accompanying figure.  Note that this structure contains five hydrogen bonds (dashed red lines), whilst the Pentamer logo on the Penta bottle contains no hydrogen bonds.
Supporters of Penta have claimed that the structure depicted on the Penta water labels should be regarded as only a convenient logo and not a scientific claim.  If this distinction exists, it is not made clear on the label.  However, there are many examples of non-scientific depictions of molecules on the labels of a variety of household products.

## Hydration
It is difficult to determine whether Penta is consistently claiming that their product offers improved hydration.
In the past, the official Penta website made specific claims on its What makes Penta unique? page, section heading Proven More Effective Hydration, that the altered structure speeded cell hydration via aquaporin transport. For instance, the page for Jun 04 2003  features a diagram showing stylised pentamers entering a cell and states
Currently on the same page, this is apparently contradicted by the text
Confusingly, the (now defunct) equivalent page of the British Penta website features the diagram and the earlier more explicit claims
It is unclear as to why water more easily penetrating cell membranes is nessesarily a good thing. Cells maintain themselves in a careful homeostasis. Water that behaved in the way claimed of penta-water would probably be poisonous, rather than healthful.

# Peer-reviewed papers quoted by Penta

## Raman spectroscopy
This subsection concerns the (published and peer-reviewed) paper.
In this paper the authors examine a peak in the Raman spectrum at a wavelength around 650 nm for various liquid water samples.  The samples include several types of distilled water and Penta Water.  The authors claim that the relative position and width of the peak for Penta compared to other waters is evidence for Penta being a new structure of water.
Graphs of the results can be found at a Bio Hydration Research Labs website .  From these, it is seen that the difference between the two distilled water samples Distilled 1 and Distilled 2 is similar in size to the difference between either and the Penta sample.  The authors do not provide an explanation as to why only the Penta to Distilled 1 /Distilled 2 difference is evidence for a new structure of water, whilst the difference between the distilled waters is presumably due to impurities.  However, supporters of Penta argue that data showing peaks for Penta samples at >658.8 nm, compared to the other samples are below 658.4 nm is a significant and meaningful difference.
The authors also find that the effective cluster temperature of the Penta water samples are 12 C higher than the control samples.  In other words, they observe that the Penta water samples behave similarly to normal water that is heated by an extra 12 degrees (though the actual measurable temperature of the water remains the same).  This appears to be inconsistent with the claimed higher boiling point of Penta Water. (If normal water boils at 100 C, then one might expect Penta water to boil at 88 C due to its claimed effective higher temperature.)
These were not double blind measurements.  The Penta water samples were provided by Bio Hydration Research Labs.  Supporters of Penta point out that the vast majority of sample analysis experiments are not performed double-blinded.  However, it should be noted that double-blinded experiments are generally to be preferred in cases where the differences between samples is small, and in the cases where any difference between samples is likely to prove highly controversial.
This paper is available from the AquaPhotonics website. 

## COM crystals
This subsection concerns the (published and peer-reviewed) paper
In this paper, the authors find that calcium oxalate crystals (which can form kidney stones) dissolve 3X faster in samples of Penta compared to the rate in distilled water.  The rate in Penta water is found to be 0.47 nanometers per second, which is roughly 0.04 mm per day.  It would take approximately 4 months at this rate to dissolve a 10 mm stone.
These were not double blind measurements.

# Associated organizations
- Bio Hydration Research Labs manufactures Penta water.  They are located in Carlsbad California.  The CEO is Bill Holloway.  G. R. Holloway, wife of Bill Holloway is the President and co-founder.  Their son, Michael Holloway is also a co-founder and sits on the board of directors.  Others on the board include Dr Nikolai I. Tankovich and David Cheatham. 
- AquaPhotonics is a biotechnology company in Carlsbad California that makes extensive use of Penta in their products and appears to be a sister company to Bio Hydration Research Labs.  Dr Nikolai I. Tankovich is the CEO and David Cheatham is the president.  Bill Holloway, G. R. Holloway and Tommy Thompson (who was the Secretary for Health and Human Services for President George W. Bush) sit on the board of directors.
- Diamics is a company dealing in medical diagnostics technology that has distribution rights for AquaRX (or Penta) water in diagnostic markets, claiming that its properties give cell samples "longer shelf life, better maintenance of cellular structure and improved performance in molecular assays". 

# Positive reviews
Penta Water has received much positive publicity in the press and has received positive reviews from health-oriented websites (e.g. ).  There are also numerous testimonials from the public and endorsements from celebrities (e.g. Sting and Farrah Fawcett ) who have stated  that they have enjoyed or benefitted from drinking Penta Water (though there is no independent verification of these endorsements).
The official Penta site also carries many testimonials from successful sports-people  including Olympic contestants and medalists.
Testimonials such as the above are known by scientists as anecdotal evidence.  Mainstream science generally places little weight on anecdotal evidence because it is known that people can be (unintentionally) unreliable witnesses of subtle phenomena, such as health improvements after taking a proposed cure. Furthermore, Penta's stated promotional system ("Initially a trial sample of Penta will be sent to select teams or sports people. Following a successful trial a special rate is offered.") could be interpreted as targeting athletes who are already successful or improving.
Penta is a sponsor of the National Fibromyalgia Association (U.S.) website and is endorsed by them for being the "purest known bottled water on the market" .
Donald MacLaren, in the physiology department of Liverpool John Moores University in Britain is doing research for Penta and was quoted on their now defunct website as stating
These studies have yet to be published in a peer-reviewed academic journal.
Jorge Cruise, author of The 3-Hour Diet has recommended Penta water as "one of the keys to weight loss" , even though there have been no peer-reviewed studies in any academic journal that show this.