SAS E-Bulletin-- Week of August 3, 2001
compiled and edited by Shawn Carlson
Lab Notes
LN1: A Safe Source of High Current
by Kevin Kilty
Several years ago I developed a technical course for industry. The objective of the course was to train manufacturing operators in the physics, chemistry, and engineering of their machines and manufacturing processes. The course was based on demonstrations, and for many of these I required a source of rather large current.
The pistol-grip soldering gun, typified by the style originally offered by the Weller Company, makes a very convenient source of current. The soldering gun is, in effect, a power transformer with a large ratio of primary to secondary turns, and very heavy secondary windings. My particular gun is rated at 100 Watts (input power), and has a turn ratio of 170. When plugged into a 120Vac outlet it will produce 0.7Vac on its output terminals open circuit. To turn this into a current source, simply remove the heating element from the gun and replace it with two very heavy copper conductors, I suggest copper tubing, to convey the current. The device is very safe. An output potential of only 0.7Vac presents no shock hazard at all, and the only conceivable danger from this current source is that a very short output circuit path, one with too little capability to dissipate heat, could become hot and cause a burn. The gun has enough resistance internally within its secondary winding (at least 5 milliOhms) to make it impossible to short-circuit.
Transformers are very efficient electrical devices, and it seems reasonable to suppose that even an inexpensive soldering gun is 95% efficient or thereabout. With 100Watts input it draws 833mA from the wall outlet, and could deliver approximately (.95)(0.833)(170)=134 Amps at its output terminals when they are short circuited. In reality it is very difficult to deliver this amount of current for the reason that practically any contact resistance at the output terminals is a major impediment to output current--remember that the soldering gun has an output potential of only 0.7Vac. I personally have never obtained more than about 100Amps from my gun. A higher wattage rated gun can deliver more current, but the problem of minimizing contact resistance becomes even more acute.
One use to which I put my "current
gun" was to demonstrate the operation of a household circuit
breaker. I cut away one side of a 15 Amp circuit breaker and replaced
it with clear acrylic so that the mechanism was clearly visible.
I then fabricated two heavy conductors to which I could easily
connect the terminals of the soldering gun. Pulling the trigger
and delivering 65-70 Amps will cause a circuit breaker to trip
within 15 seconds. By varying the contact resistance slightly,
a person can lower the current through the breaker. It is interesting
to demonstrate that a small over-current, say 20 Amps, takes a
long time to trip the breaker. It is a vivid illustration that
circuit breakers provide absolutely no protection for personnel
who become short circuit paths to ground.
Comment: What a great idea! Now, if you want to do electroplating, electrotrolysis, or annodize aluminum what you need is a DC high current source, typically in the 20 amp range. Kevin's excellent insight suggests that by rectifying the voltage and perhaps stepping it up a little, one might be able to use a soldering gun as the first element in a cheap DC current source. (I've paid up to $150 at a surplus dealer for a 40 amp model.) I'll leave the details for you to explore. If you make one work please send in the design and describe your experiences so we can share them with the rest of the membership. SC
LN2: Diathermy in the Lab
by Ely Silk
No, not for tired muscles or aching joints.
As a low-cost means for producing free radicals, electrodeless
spectral sources, and plasma-enhanced chemical vapor deposition
(PECVD), diathermy can't be beat. If you need to coat surfaces
with microthin layers of diamond or grow carbon nanotubes for
fun and profit, consider purchasing a used, vacuum-tube short-wave
diathermy device. These units operate at 27.120 MHz at less than
100 watts. Auction sites on the Internet are a good place to start
hunting, but make sure you get a vacuum tube rf unit and not an
earlier Tesla device.
First, snip off the conductive rubber pads from the two cables
and replace them with large alligator clips. Next, you will need
a 1" diameter x 16" long pyrex tube. A small vacuum
pump capable of pumping down to 100 millitorr is adequate to start
with. You will require plugs and tubing to allow pumping the system.
Loosely wrap two bands of 1/2" wide copper foil about 3"
apart near the center of the tube leaving small lips for the alligator
clips. Leave a small, even gap all around between the foil and
the tube.
Pump down the tube, then turn on the diathermy
and tune it until there is an intense, glowing plasma in the tube.
Play with vacuum levels and tuning until you are comfortable with
the mechanics of the process. If the tube doesn't fire, shut off
the diathermy and move the bands a little closer together. If
the tube fires easily but gets too hot, spread the bands apart
after shutting the diathermy unit. The pyrex tube (as well as
the cables, foil electrodes, and clips) will normally get very
hot and the tube may soften during extended operation. (Note:
Quartz is superior to Pyrex, but you will have to contend with
UV protection.) Observe all safety precautions in working with
high vacuum and rf power.
Scientific Photography
Here's Ely Silk's description about how it took his fantastic photos of flagella of soil bacteria which he submitted in SAS's first member photo contest. Enjoy. SC
BACTERIAL FLAGELLA: How I Photographed Them
by Ely Silk
I placed several grams of garden soil in a beaker of diluted nutrient broth used for culturing bacteria. The culture was left at room temperature overnight. The next day, after checking a drop of culture for active, motile bacteria, I streaked a nutrient agar Petri dish with some broth. Twenty four hours later, colonies were checked for motile bacteria. If the bacteria do not actively move, chances are they do not have flagella. One needs to obtain specimens within one to two days of culturing. The inhabitants of older colonies lose their flagella. I sampled several active colonies and placed the combined samples in a drop of distilled water on a very clean microscope slide. After the drop dried, I placed the slide in a Coplin jar filled with methanol for one minute. This gently fixed the bacteria and helped them adhere to the slide. (Alternatively, the film can be fixed by quickly passing the slide, film side up, through a gas flame. I prefer the alcohol treatment.)
The following procedure is based on that given in Bacterial Cell Culture - Essential Data by A.S. Ball. [Buy it online from SAS at 25 percent off. SC] A mordant is used to first 'coat' the bacterial flagella and prepare these ultra thin structures (10 to 50 nanometers in width) to bind with a silver stain. This is prepared fresh as follows:
Picric acid (saturated solution) 10 ml Tannic acid 5 grams Ferrous sulfate 7.5 grams Distilled water 90 ml
Mix well and filter before use. Discard unused solution at the end of the day. [Your SAS membership gives you access to these chemicals discussed in this note, and at 10 percent discount. Contact Nancy for details. SC]
After fixing the bacterial film, flood the slide with the filtered mordant for 5 minutes. Wash the slide in distilled water.
A sensitized silver nitrate staining solution is prepared next. It is formulated by combining silver nitrate solution and ammonium hydroxide. Prepare a small quantity of the solution using the technique outlined in the given reference. Discard any unused solution at the end of the day by pouring it into a large beaker of very dilute hydrochloric acid, then pouring that down the drain. Silver nitrate in ammonia can produce explosive compounds if allowed to sit around too long or evaporate!
The mordant causes the flagella to swell and the treated flagella will reduce the sensitized silver nitrate. In effect, you are plating the thickened flagella with silver. Wash, dry gently, and mount in a suitable medium. Examine under oil immersion.
Do not expect that many of your slides will
be successful. This process is hit and miss. I chose a successful
slide, photographed it using a monochrome CCD video camera and
captured the image using a Snappy image grabber. Note: There is
a way to observe flagella moving on living, unfixed bacteria,
but that's another Lab Note entirely.
The Mind of a Theorist
The Return
by George E. Hrabovsky, President of MAST
The News
Well, hello again, this time in a new format. I have to admit that I have never written a piece for electronic-only dissemination. It is good to be contributing to SAS again. My columns will be, from now on (assuming you all like the new content) in three parts: I will have a brief news piece (either MAST news that bears on theory, and announcement of some new and important theoretical breakthrough, or something that triggers a response from general news), some demonstration of theory in action (similar to the lab notes that have been appearing), and a book review related to the demonstration.
I will be writing this column in Mathematica and then converting it to HTML for publication in the Bulletin and to my web site, www.madscitech.org. Simply look for the link to The Mind of a Theorist.
Demonstration: Proving Something to be a Group
Some time ago I wrote a column on symmetry and why this fascinating subject is important. The bottom line was that if something is symmetrical then there is some reason to believe that there is a conservation law at work somewhere. How do we find whether something is symmetrical? One way is to show that it forms a symmetry group. I will explore this special type of group in my next column. In this column I will show you how to prove something is a group, this will lay the ground-work for my next column.
As you no doubt know by now any collection of things is naively a set. The elements of such sets can be combined two at a time, an example of this is addition. Such combinations are called binary relations. Any set whose elements are combined by a binary relation is called an algebraic structure. We will use the symbol ⊕ to denote such relations. Let us use addition as our binary relation. We can now choose what sets we want to work with. Let us choose two sets; the set of natural numbers,
and the set of integers,
The simplest type of algebraic structure has two special properties for its binary relations. The first is the requirement that any results from the relation must also be members of the set, this is called closure. We can write this symbolically using x and y as elements of the set S,
We can immediately apply this to our two example sets. We simply ask the question, "If we add two elements of these sets, do we get another element of these sets?" In both cases the answer is clearly yes.
The second requirement is that when we apply the binary relation to three elements, it does not matter which pair we relate first, this property is called associativity. Symbolically this can be written,
We can immediately apply this to our two example sets. We simply ask the question, "Is addition associative on these sets?" In both cases the answer is yes. This is well established from our study of elementary algebra in high school. Such an algebraic structure is called a semigroup. Under addition we can say that both the set of natural numbers and the set of integers form a semigroup.
A third requirement can be added to our semigroup. If we state that there must be an element such that the application of our binary relation between that element and any other element of the set leave that other element unchanged, we have established an identity element. This can be written symbolically as,
Any semigroup meeting this requirement is called a monoid. We can apply this to our two semigroups, "Do these semigroups have an identity element?" We recall that the identity element for addition is 0. The set of natural numbers does not have this element, though the set of integers does. What conclusion can we reach from this? The set of natural numbers is not a monoid, while the set of integers is.
If we have a monoid, we can check for another requirement. If we state that there must be an element such that the application of our binary relation between that element and any other element of the set gives us the identity element, we have established an inverse element. This can be written symbolically as,
Any monoid meeting this requirement is called a group. We can apply this to our monoid, "Does the monoid of the set of integers under addition have an inverse element?" The answer is yes, thus the set of integers is a group under addition.
In the next column I will present the idea of a symmetry group.
Book Review
The subject of groups is a part of the discipline called abstract algebra. It is a generalization of the basic notions of algebra we went through in high school. The best book that is accessible to people is the subject of this review:
Algebra, 3rd Edition, Saunders MacLane and Garrett Birkhoff, Published in 1993 by AMS-Chelsea. This book begins with a detailed study of the algebra of sets, functions, and numbers. Then it builds on these ideas to study such algebraic structures as groups, rings, vector spaces, and many more. This is my favorite book on algebra. It has LOTS of practice problems in a nice balance between actual calculations and proofs. Be prepared to work hard. If you do put the work in, it is immensely rewarding and you will come away with a deep understanding of these concepts. All aspects of algebra are being applied to physics, so this subject area is a must for theorists.
Converted by Mathematica July 24, 2001
The Search for F. B. Lee
As you recall from last week, F. B. Lee is, well, God. He's the fellow who created the particle accelerator projects (and others) that so many old-timers remember from The Amateur Scientist column of the 1950's and 60's. I didn't even know the gentleman's first name. I asked for the membership to help track this fellow down, and boy did you all ever respond.
It turns out that in 1960, Franklin B. Lee founded a company called Science First which does about a million dollars a year worth of business selling hands-on science labs for education, home and industry. Lee, now 84, is still with us and his company is now run by his daughter. Lee carried out an extensive correspondence with Steve Hanson of the Bell Jar and Steve has excerpted from that correspondence to produce a nice retrospective on Lee's life. It makes for delightful reading.
The person who answered the phone at Science First assured me that Mr. Lee doesn't have email and is rarely in the office. So if anyone out there want's to contact him, (perhaps to tell him how much his projects in The Amateur Scientist meant to you), you need to do it by regular mail sent to him care of Science First. In the meantime, Science First has posted us a catalog and we hope to be able to offer their products to SAS members soon, at a discount. (But we haven't entered any formal negotiations yet, so no promises. I'll update you on this soon.) And I'll send a letter to contact Mr. Lee myself soon and let you know what, if any links I can forge between SAS and Science First.
 |
The man himself... Franklin B. Lee. Inventor, entrepreneur and icon of innovation for a generation of amateur scientists. |
Thank you to everyone who responded!
Exploring New Ways of Using the Web for Citizen Research-- A Suggestion from Web Expert Steve Crandall
[Steve Crandall is a Web expert who works at AT&T researching new ideas for using the Web in ever more powerful and interesting ways. He is personally responsible for AT&T providing SAS Local Chapters will free web access. He recently called me to discuss a new innovative Web-based information sharing concept that, I must admit, sounded great. So I asked him to describe the idea so the entire membership could comment. Here's his description. I've started a discussion about this on the SAS Forum. Please feel free to post your comments there and I'll share selected responses with the rest of the membership through the E-Bulletin. SC]
A potentially interesting project would be to build a website that would be a repository for links to interesting data. An enormous amount of data are posted to the web, but much of it is difficult to find and often useless to anyone other than a specialist. Even more useful would be a mechanism to alert amateurs to interesting transient phenomena.
An outstanding example of this type of site is Spaceweather. In addition to links relevant to solar astronomy and weather, it offers nice descriptions, alerts (flares, aurorae, etc) and even photography submitted by amateurs. The site is very active and is worth visiting daily (be sure and check out the helioseismic holography).
Over time one could imagine assembling a site with links to places like spaceweather as well as building important resources where such sites do not exist. One might start by trying to assemble the best of the earthquake sites and perhaps build some display tools.
It should be noted that some people have
built clients that access data sites (this is particularly common
in for meteorology and Solscape X for Mac OS X is a clientized
version of spaceweather). These can be interesting exercises and
can be useful for near real time alerts, but a web interface makes
more sense and one could offer
email alerts.
Steve Crandall
esc@research.att.com
scrandall@telocity.com
Q & A: Temperature Standards
Questions: I am in the process of assembling pieces to build the platinum thermometer project from the March, 1999 edition of The Amateur Scientist. I will eventually need to build some standard cells to calibrate it with. So here are the questions:
1) Do you still have the small glass balls used to fill the thermometer? I don't need the kit, just the small glass balls.
2) Is the water triple point cell still available?
3) Is the mercury freezing point cell still available?
4) Can I order very pure mercury from you to go with the mercury freezing cell?
5) Can you get very pure tin? Say 500 grams or so?
Thanks,
Answers:
Hi Bob. Thanks for asking. Here are the answers to your questions.
1) About the glass beads. The beads must be very tiny indeed so that they effectively form a continuous surface over the sensor. George Schmermund, the fellow who designed the thermometer, breaks up borosilicate (Pyrex) glass and grinds it up in his ball mill. Then he passes the result though a two wire screen of 100 and 150 mesh and keeps what remains between the screens. That's a lot of work. It's a lot easier to go to a shop that uses or sells sand blasting equipment and secure from them some fine silica sand, dry it thoroughly by baking in an oven at 350 degrees, and then sift that. Make sure the tap the grains down into the thermometer tip using a vibrator to make sure they are well compacted. Larger gains can be used above to fill up the body of the thermometer. (And by the way, George is willing to make the thermometer kits available again provided there's enough interest to do so. So readers should check out the article through the above link and let me know if you'd like to purchase a complete kit.)
2) About the triple point cell, yes and no. The original triple point cell is no longer available but George has dramatically improved the design and his improved version is available. Of course, with improved ease of use, durability and performance also comes in enhanced price. The new unit is a dream to use and a delight to look at, and it retails for $350. Of course, your SAS Membership entitles you to a substantial discount. The member price is just $310. And that really is a bargain, considering that the low end professional units are, in my view, far inferior to the Schmermund Triple Point Cell and those start at $1000.
3) About the Mercury Freezing Cell, again yes they are available too. They contain everything you need (except the mercury itself) to establish the freezing point of mercury. The retail price is $150, but we can offer it to SAS members for just $95. It's not in the on-line store yet, but if you want one just let Nancy know and she'll get one to you.
4) Yes, we can get you very pure (99.9999 percent) mercury. But you'll spend a lot less money if you purchase the lower grade and zone purification it if you need to. (For a discussion on zone purification see last week's E-Bulletin.) We can get you whatever you want. Just work out the details with Nancy.
5) Can we get very pure tin? But of course! Sounds like you're setting your sites on making a melting point of tin standard. Again, the trail blazer here is George Schmermund. You can find a tiny fraction of his products on his Web site at www.cheapscience.com. And if you're really interested in temperature, check out his auctions on Ebay.com. You'll need to do a seller search for "mesotek." (Click the search button, and then select the "seller" option.) I recommend you look into his melting point of Indium standard of you want to really develop an appreciation for what it takes to do this work to extremely high precision. Astonishing!
Feedback
Non-Support of Amateur Cosmology
Dear Shawn,
I strongly agree with your position on these issues, and I was
very interested in your experiences.
I joined a news letter on Tesla coils some years back, because
I had an interest in the subject that remained from my High School
days in the 1950's. I enjoyed the technical articles, but was
amazed to see that a very non-scientific sort of cult had developed
around Tesla. I wound up getting on mailing lists for various
meetings and conventions that seemed to deal with Tesla and life
forces or something, and because I had an M.D. after my name on
the member list, received a couple of personal letters from members
about the "healing powers of Tesla's great invention".
Some felt Tesla was about to make new "breakthroughs"
but had been sabotaged by industrial interests.
Some of these same personalities seem to be attracted to cosmology
and unified field theory. I share your observations about the
delusional aspects of some of these people and their intolerance
of criticism. Debating these things would start a never ending
non-productive morass of speculation that we should avoid in this
group.
Good luck to you in your new location and with your new projects.
Bill Parker
==
Dear Shawn,
I agree and sympathize totally with your position. Even Ph.D's are not immune to self-deception, witness the cold fusion fiasco.
==
Shawn
Your reply on cosmology, creation & TOE had me laughing in tears!
Keep Up the Good Work.
==
Dear Shawn,
In the latest E-Bulletin you write..
"You should have seen his reactions to even the most GENITAL of criticisms. He really scared me."
Thought this must be a typo- unless you were trying to scare him too ;-}
By the way, I thoroughly agree with the policy of excluding amateur cosmology. I've had to deal with these crazies from time to time. It's unfortunate, because there could be a lively forum for discussion on this topic by knowledgeable individuals. The difficulty always seems to be that wide-eyed proselyte that isn't bothered by facts, who dominates the dialog because any hesitation might let one of those nasty "fact-mongerers" make a contradictory point. These folks have made some of the astronomy newsgroups uninhabitable.
Keep up the good work!
Response: Fred, ooops. Thanks for accepting the error with humor. The E-Bulletin hadn't been posted more than 10 minutes before the first email message came in alerting me to this spell checking glitch. I fixed the problem promptly. Sorry if anyone was offended by the miscue.
And thanks to all for your understanding and support of the SAS position of non-support for amateur theories of creation, cosmology, and unified field theories.
SC
Secrets of Zone Purification
Shawn,
I have heard the story about the Native Americans freezing of maple sap to produce syrup also. One of my maple trees once got damaged around the time of sap flow, which is in the spring when the days are above freezing and the nights are below freezing, during the night the leaking sap froze into an icicle. The kids found it the next morning and said it was delicious.
I am certain that the boiling process changes the syrup but I also think the changes might be for the better in terms of taste. We have boiled sap down a couple of times and there seems to be a woody taste (that I don't like) that goes away when the sap is cooked down the right amount. You have to get rid of a lot of water so the freezing method could require dealing with large amounts of frozen sap. It seems like 4 or 5 gallons of sap gives about a quart of syrup. I suppose I could try some freezing experiments and even some experiments in vacuum evaporation next spring.
One more thing. Cooking destroys the micro organisms that are certain to be in the sap. I put my syrup in a bottle while it was still hot and it has stayed mold free for several months.
Response: Great story and observations. Re. cooking destroying micro organisms, good point! But it's extremely difficult to grow micro organisms in honey for a variety of reasons (a fact bees are quite happy about). Now, my wife (a native New Englander) assures me that she has observed mold growing on the surface of maple syrup that had been left out for several days. Nevertheless, concentrated maple syrup may not be a good growth medium either. My family has never followed sanitary protocols when pouring it over morning pancakes and we've never had any go bad on us. Of course, we do keep it in the refrigerator, a precaution we don't take with honey. Hummm... I see another interesting avenue for amateur experimentation! (BTW: Here's an interesting thing to ponder. Why doesn't mold grow on candy?)
SC
E-Bulletin Format
Dear SAS,
I enjoy the Bulletin and am glad that you are able to make it available to more people through the internet. However, I use a laptop computer and am often not able to connect to the internet, so I was wondering if there was a way that you could also post a downloadable .pdf or even .html file on the internet so that people could download the Bulletin for off-line viewing. I appreciate the Bulletin greatly and I understand that you have a lot to do, but I just thought that making the Bulletin available off-line could make it easier for some people (such as me) to really investigate the articles.
Thank You,
Response: Thanks for the suggestion, Chris. Anyone can capture the page from the Web by using the save command in their browser. But putting in the individual images, although doable, would be a pain. So how important is this to everyone? Please let me know if this is a service you would actively enjoy if we were to provide it.
SC
Kudos
Shawn, I think you have found the "business model" for SAS! Providing quality products and information for people with the passion for amateur science.
Featured Products
We've got so many featured products this week that I've decided to put them into separate links.
Glassware Galore! Our glassware is a hit. You've been buying it up so fast that you're giving Nancy fits trying to keep up with the orders. Well this week, let's try to drive her really crazy! I've added scores of new lab glass to our list. With still more coming next week. Most at 50 percent off bulk rate prices!
Books We've got another great crop of books to choose from. Check out this week's lineup.
SAS News
Tinkers Guild / SAS Office Consolidation is Underway, at Long Long Last!
Sheldon and Denise arrived in Rhode Island and took possession of their beautiful home on Tuesday. (Sorry Californians. They purchased their two-year old home, with 3 br, 2 1/2 baths, two stories with deck and workshop and garage, quietly tucked away from the road on 3 wooded acres, for just $200,000. And so you see another reason Michelle and I chose to relocate to Rhode Island...) Sheldon's been in the office since Thursday and things are starting to shape up a bit. It will take weeks for everything to settle in and get Tinkers Guild and SAS working in real synergy. But some great things have already started happening. I'll keep you posted.
Amateur Scientist's Workshop Update: NSF Preliminary Proposal Filed
This week we also filed a preliminary proposal with the National Science Foundation to help fund the production of The Amateur Scientist's Workshop TV series. I must thank Elizabeth Rollins whose Herculean efforts created an outstanding preliminary proposal. She really carried this project forwards and deserves all the credit for a job extremely well done! You have no idea how fortunate I feel to be blessed with such gifted and capable partners. This was enormously difficult, and now I know that the NSF will consider our show very seriously.
Can You Explain This. . . About Salt? Answers From Last Week
Last week's E-Bulletin contained the following two challenges.
First, briefly, why do salts generally lower the temperature of fluids when they dissolve? This is an easy one. The dissolution of salt is endothermic. That means that it is favored by entropy (a solution of salt ions has higher entropy than salt crystals sitting undissolved in the solution), but it takes energy to make it happen. That energy is supplied by the kinetic energy of the molecules of the solvent. As they slow down, the solvent cools down.
The second challenge is a bit more interesting: Here's the complete text that appeared last week...
"And here's a simple experiment that can be performed as a parlor trick. Float an ice cube in a glass of water. Have a shaker of salt within arm's reach. Hand someone a paper match and challenge him to remove the ice cube from the water without lifting it with any implement other than the match. When he gives up, bend the head of the match to a right angle, place the body of the match flat on top of the ice and cover it with a thin layer of salt. The match will promptly freeze to the cube. Lift the cube from the glass by the head of the match."
I hope you tried it, because this is a fun and really quite interesting experiment. If you did, then you may have noticed on close inspection that the salt melted some ice all around the edge of the match. The energy required to liberate the sodium and chlorine ions in the thin film of melt-water must be supplied by the ice itself. Replacement energy then flowed from the region under the match that was protected from the salt. As a result the temperature of the film of fresh water in contact with the lower surface of the match dropped below its freezing point and turned into ice that cemented the cube to the match.
Cool, eh?
Parting Shot
Here's a wonderful news story sent in by Steve Crandall. It appears that our President has an unappreciated talent in theoretical physics. But why don't you read the story, and make up your own mind?