If you take out your household thermometer and examine its packaging, you will probably see a note that indicates that the thermometer “conforms to ASTM E667.” This gibberish refers to the fact that all U.S. manufacturers of thermometers have voluntarily agreed to meet the standards of the American Society for Testing and Materials, an organization that sets standards for many products and services. ASTM is a nonprofit educational association, founded in 1898, that publishes over 7000 separate documents detailing standards in fields ranging from steel and chemicals to robotics, medical devices, and child-resistant packaging. Committees, comprised of volunteers, contribute their time to set standards, and ASTM bylaws require that a majority of committee members may not be comprised of producers of the item for which the standards are being set.
The ASTM specifies that clinical thermometers have constrictions, and there is no reason for the industry to want to change the technology; after all, the constriction is cheap and efficient and requires no moving or mechanical parts that could fail to keep the mercury from returning to the bulb. The ASTM standards also help explain why all thermometer scales look so much alike. All clinical thermometers are expected to have scales ranging from at least 96 to 106° Fahrenheit, and graduated in 0.2-degree Fahrenheit intervals. The only long lines allowed on the temperature scale are full-degree gradations and, at the producer’s option, the 98.6° designation.
The ASTM also sets minimum standards for the accuracy of clinical thermometers, in degrees Fahrenheit:
* * *
Temperature Range
Maximum Error
>96.4
0.4
96.4 to 97.9
0.3
98.0 to 101.9
0.2
102.0 to 106
0.3
<106
0.4
* * *
A clinical thermometer is designed to retain the body temperature of the user until it is reset, but a thermometer will respond to hotter temperatures. Many a thermometer has been broken in the mistaken belief that it is best to rinse off the bulb by using extremely hot water.
* * *
HOW DO THEY MEASURE THE
VITAMIN CONTENT OF FOODS?
* * *
Some vitamins are present in such small concentrations in food that there are only a few micrograms (millionths of a gram) of the vitamin per hundred grams of food, while other vitamins might constitute ten milligrams per hundred grams of food. The techniques that work to measure the abundant vitamin often won’t work to evaluate the presence of the other.
Jacob Exler, nutritionist for the Nutrient Data Research Branch of the Human Nutrition Information Service, told Imponderables that there are two types of analytical procedures to measure the vitamin content of foods, chemical and microbiological:
The chemical procedures measure the actual amount of a vitamin or a derivative of the vitamin, and the microbiological procedures measure the biological activity of the vitamin on some selected organism.
Today, chemical procedures are in vogue. In the past, microbiological studies were more common, and researchers tested not only on bacteria but on live rats. In fact, as late as the 1970s, the FDA used approximately twenty thousand rats a year just to test foods for vitamin D content! Roger E. Coleman, of the National Food Processors Association, explains the theory behind microbiological studies:
An older but still very acceptable method for vitamin assay is to measure the amount of microbiological growth a food supports. There are certain bacteria that require an outside source of one or more vitamins to grow. The growth of these bacteria is proportional to the amount of the required vitamin in the food.
But microbiological work is extremely sensitive. If conditions are not perfect, results can be skewed. As an example, an article in FDA Papers states that “the organism used for measuring vitamin B12 activity will show a measurable response when dosed with less than one ten-billionth of a gram of the vitamin.” Microbiological assays work more effectively than chemical methods for measuring B12 levels (and some other vitamins, such as biotin, B6) because chemical analysis isn’t sensitive enough to respond to the minute amounts of the vitamin contained in food.
In a chemical analysis, each vitamin in a given food must be measured separately. There are many chemical procedures to choose from, with catchy names like “gas-liquid chromatography” and “infrared spectroscopy.” Coleman explains a few different types of chemical analysis that are a little more comprehensible:
Each measuring technique is based on a property of the vitamin. For example, riboflavin fluoresces [produces light when exposed to radiant energy] and is measured by a fluorometer or fluorescence detector. Vitamin C combines with a certain purple dye and makes it colorless. By measuring the amount of this dye that is changed from purple to colorless, we can calculate the amount of vitamin C present.
Despite the high-tech names, chemical analysis microbiological methods, but it is cheaper and faster—and doesn’t necessitate twenty thousand rats a year sacrificing their life for vitamin D.
Submitted by Violet Wright of Hobbes, New Mexico.
Thanks also to Todd Grooten of Kalamazoo, Michigan.
* * *
HELP!!!
* * *
If Richard Feynman and Albert Einstein can’t stamp out all the Imponderables of the world, do you expect us to do it? But we’re nothing if not persistent. Keep sending in your Imponderables about every conceivable subject—they’re the lifeblood of these books.
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Although we accept “snail mail,” we strongly encourage you to e-mail us if possible. Because of the volume of mail, we can’t always provide a personal response to every letter, but we’ll try—a self-addressed stamped envelope doesn’t hurt. We’re much better about answering e-mail, although we fall behind when we’re in heavy work mode.
Come visit us online at the Imponderables Web site, where you can pose Imponderables, read our blog, and find out what’s happening at Imponderables Central. Send your correspondence, along with your name, address, and (optional) phone number to:
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* * *
About the Author
DAVID FELDMAN is the author of ten previous volumes of Imponderables®. He has a master’s degree in popular culture from Bowling Green State University in Ohio and consults and lectures on the media. He lives in New York City.
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Copyright
This material has previously appeared in David Feldman’s Imponderables® series.
IMPONDERABLES®: SCIENCE. Copyright © 2006 by David Feldman. All rights reserved under International and Pan-American Copyright Conventions. By payment of the required fees, you have been granted the non-exclusive, non-transferable right to access and read the text of this e-book on-screen. No part of this text may be reproduced, transmitted, down-loaded, decompiled, reverse engineered, or stored in or introduced into any information storage and retrieval system, in any form or by any means, whether electronic or mechanical, now known or hereinafter invented, without the express written permission of HarperCollins e-books.
EPub © Edition SEPTEMBER 2006 ISBN: 9780061983771
ISBN-10: 0-06-089886-0
ISBN-13: 978-0-06089886-1
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