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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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|February 1952 Radio & Television News|
[Table of Contents]
These articles are scanned and OCRed from old editions of the Radio & Television News magazine. Here is a list of the Radio & Television News articles I have already posted. All copyrights are hereby acknowledged.
Carbon tetrachloride (CCl4) was a common cleaning agent used commercially through about the early 1950s when it began receiving a lot of bad press due to a linkage to severe kidney damage from exposure even in vapor form. I notice that Mac mentions having read an article about the potential danger of 'carbon-tet' in an edition of Radio & Television News, not coincidentally the publication where the "Mac's Radio Service Shop" series appears. He also mentions a publication called International Projectionist (see thumbnail at left), which included instructions for cleaning movie film with carbon tetrachloride, and had a warning about health risks. Dry cleaners were big users, as were industrial production facilities because of its exceptional degreasing properties.
Lots of cleaning agents have come and gone over the years. Back in the early 1980s while working for Westinghouse Oceanic Division in Annapolis, Maryland, we routinely used methyl ethyl chloride (MEK) to clean flux off PC boards and for removing lacquer coatings from components and markings. Sometime around 1984-85 or so it was withdrawn from use due to having been placed on the suspected carcinogen list. Today and for the last two decades, I have been buying MEK at Home Depot and using it for cleaning parts prior to painting, so evidently a government panel somewhere has decided it is not as dangerous as originally thought.
Mac's Radio Service Shop: Carbon-Tet Can Kill
By John T. Frye
"Hey, Barney," Mac's muffled voice came from behind the closed door of the chassis-cleaning closet, "step outside and see if you can smell any carbon-tet fumes at this exhaust-fan port."
The apprentice technician of Mac's Radio Service Shop went out into the alley and sniffed cautiously at the strong current of air being pushed out by the fan. "Sure can," he called; "where's it coming from?"
"Come on back in here and see," Mac invited.
When Barney opened the door of the cleaning closet, he immediately noticed some changes. For one thing, a sort of metal funnel was mounted with its large opening pointing directly toward the exhaust fan and only a couple of inches away from it. From the smaller end of the funnel a piece of down-spouting went down along the wall and terminated in a ninety-degree elbow that rested on the floor. In front of the open mouth of this elbow was a piece of gauze that had been soaked in carbon tetrachloride. Replying to the boy's questioning look Mac explained:
"Carbon-tet fumes are five times as heavy as air; so I cooked up this arrangement to pull them right off the floor without interfering too much with the sucking out of dust from the top of the room. That fact that you could detect the carbon-tet vapor outside while I could smell none of it in here shows that the system is working."
"And that's good?"
"I'll say it's good. Just recently I've had my eyes opened to just how dangerous breathing carbon-tet fumes can be; and when I think of how carelessly we have been using the stuff in the past, I feel like a man who has just found out that the make-shift poker he has been using to stir the fire is really a stick of dynamite."
"How did you get hep to all this?"
"I had a little 'hint' published in Radio & Television News" that involved the use of the cleaning fluid. That brought me a letter from an instructor at the Coast Guard Institute asking if I was aware of the very real danger that lurked in the improper use of the chemical - a danger that he had seen demonstrated very tragically. Naturally, I asked him for more information; and at the same time I wrote to the American Medical Association and to one of the country's largest manufacturers of carbon-tetrachloride for their opinions. I also mentioned what I was doing to Dick Rider, the operator down at the State Theater, and he promptly came up with some back issues of a trade magazine called "International Projectionist" that discussed the use of the cleaning agent in the operating booth. From all these sources came warnings that say substantially the same thing: carbon-tetrachloride can and will cause serious illness and death if proper precautions are not observed in its use."
"I've noticed that bottles of the stuff always carry warning labels saying you should not breathe the vapor," Barney mused; "but I never paid much attention to them. How does it get you?"
"It can do serious harm if the vapor is inhaled, if it is taken internally, if it is splashed into the eyes, or even if it is permitted to come into contact with the skin."
"Sounds like a lot of stuff to me," Barney said skeptically. "While I've never tried drinking it or splashed it into my eyes, I've inhaled a lot of vapor and have had it all over my hands lots of times, and I'm still kicking."
"You've been mighty lucky," Mac said. "One thing that has helped is that you have usually used the carbon-tet in here with the exhaust fan going, and that has kept the vapor concentration down. However, it does not take a heavy concentration to be dangerous. Doctors used to think that anything under 100 parts per million was safe, but now they think it is desirable to keep the vapor below 50 parts per million. You can get an idea of just how little this is when I tell you that a normal nose just begins to detect the odor at 79 parts per million."
"Maybe some people can take more of it than others can."
"That's quite true. In one case I read about, four men were working together using carbon-tet for cleaning purposes. The next day one of the men developed symptoms of carbon-tetrachloride poisoning. Three days later, since he was still not feeling well, he entered a hospital. Ten days later, in spite of proper medical care, he died. None of the other three men showed any ill effects."
"Then poisoning doesn't always show up right away," Barney observed.
"That's one of the treacherous things about it," Mac replied. "It is not unusual for symptoms to show up from two to eight days after exposure, and because of this the connection between the poisoning and the use of the chemical is often overlooked. But to get back to the subject of the varying reaction of people to carbon-tet, it has been discovered that certain groups of people are especially susceptible to poisoning. These groups include fat people, undernourished people, alcohol addicts, and people who suffer from diabetes, liver or kidney diseases, jaundice, pulmonary and heart disease, or peptic ulcers."
"So alcohol and carbon-tet don't mix, eh?" Barney said thoughtfully. "Boss, you had better clean the sets this afternoon. Mom hasn't noticed it yet, but her sweet cider is beginning to taste more interesting every day now, and I hit it up pretty hard after dinner. I know you wouldn't want me to take any chances."
"Well, you have already had a whiff of the vapor; so let's see if you have any of the typical symptoms of vapor-poisoning," Mac said with a grin. "The symptoms depend somewhat upon the concentration of the vapor and the duration of the exposure; but in general they are a feeling of fullness in the head, mental confusion, and headache; and then this is followed by nausea, stupor, and loss of consciousness. In severe cases there may be trouble with the vision and the coughing up of bloody mucus. If the person is not removed to a safe area promptly, death may occur because the person simply stops breathing."
"Suppose you should topple over while you were using the stuff here at the bench. What ought I to do?"
"Drag me outside into the fresh air. If I quit breathing, administer artificial respiration at once and keep at it until I start to breathe naturally again. Keep me lying down and warm. After I regain consciousness, you can give me some hot tea or coffee to drink. Of course, a doctor should be summoned at the first opportunity and the treatment turned over to him."
"Is there anything I should be careful not to do?"
"Yes; never give alcohol, fats, oils, or epinephrine to a person who has been exposed to carbon tetrachloride."
"What's the best thing to do if you accidentally get some of it in your eyes?"
"Wash them at once with large quantities of water for a period of at least fifteen minutes."
"What would you do for a person who accidentally drank some of the liquid ?"
"That would be particularly dangerous, for drinking only 3 or 4 cc of carbon-tetrachloride may cause death. The first thing to do is to cause vomiting by making the victim drink a glass of lukewarm salty or soapy water. This unpleasant but necessary procedure should be repeated at least three times to insure that all poison possible is removed from the stomach. Then a teaspoon of Epsom salts in water can be given. That is about all the layman can do outside of seeing to it that the victim is placed in the hands of a competent doctor as quickly as possible."
"What does it hurt to get carbon-tet on the skin?"
"For one thing it washes away the natural oil of the skin and results in redness, roughness, and chapping. This, in turn, impairs the skin's ability to keep out germs and microbes, and infection is likely to develop. It is especially important to keep the chemical away from cuts and burned areas on the skin, for, while it has not been definitely established, there is some evidence that the poison may be absorbed into the system through such places. Finally, some individuals display an allergy to the cleaning agent.
"If you do get some of it on the skin," Mac continued, "you should immediately wash with a mild soap and warm water. Then an ointment containing petrolatum or lanolin should be applied.
"You know, you're beginning to scare me," Barney admitted.
"You should be scared," Mac said emphatically. "Carbon-tet fumes are said to be more poisonous than chloroform. If the poisoning does not cause immediate death, it may result in permanent damage to the liver, kidneys, heart, adrenal glands, lungs, or digestive and nervous systems. There is an added danger when carbon tetrachloride is exposed to an open flame or intense heat, for then it decomposes and forms the deadly phosgene gas of warfare."
"What kind of safety rules would you recommend ?"
"Always keep carbon tetrachloride in tightly-stoppered bottles and keep the stoppers in those bottles except when you are actually extracting some of the liquid. Never use the chemical except out of doors or in a well-ventilated place, preferably one with downdraft ventilation. Never allow pads or cloths soaked with the liquid to lie around, but place them outside as soon as you are through with them. Take precautions to prevent getting the cleaner in your eyes. Avoid having the skin in contact with it for a prolonged length of time, such as would occur when carbon tetrachloride-soaked gloves are worn. Never place carbon-tet on an open flame or a hot surface. And, of course, never keep it in a medicine cabinet or with any other bottles whose contents are taken internally."
"Whew!" Barney gasped. "In view of all that, maybe it would be better just to quit using it altogether."
"Not at all," Mac denied. "Gasoline is dangerous, too, but that does not cause us to give up our automobiles and go back to the horse and buggy. Carbon-tet does a lot of jobs around a radio shop better than any other chemical agent. It is an excellent dry-cleaning fluid, metal degreaser, and rubber solvent. You can't beat it for cleaning turntable rims, wire and tape recorder heads, tuning condenser wiping contacts, or volume controls. It evaporates quickly and leaves practically no residue. Many manufacturers of turntables, recorders, TV tuners, etc., recommend its use; and there is no reason why their recommendations should not be followed; but just remember to observe common sense precautions when you are using it."
"I'll remember, Boss," Barney promised. "From now on, while I've got the cork out of that carbon-tet bottle, I'm only going to breathe out!"
Mac's Radio Service Shop Episodes on RF Cafe
This series of instructive stories was the brainchild of no other than John T. Frye, creator of the Carl and Jerry series that ran in Popular Electronics for many years. Mac's Radio Service Shop began life in Radio & Television News magazine (which itself started as simply Radio News), and then changed its name to Mac's Service Shop after the magazine became Electronics World. 'Mac' is electronics repair shop owner Mac McGregor, and Barney is his eager, if not somewhat naive, technician assistant. 'Lessons' are taught in story format with dialogs between Mac and Barney.
Posted February 4, 2016