Bob's Mailbox

Hi Bob: I was just reading your column in the Nov. 16, 2006 issue of Electronic Design ("What's All This SiO₂ Stuff, Anyhow?" p. 18) and had some insights. The silicon dioxide (SiO₂) added to foods for anti-caking is a little bit different from sand. Chemically, it's the same, but it's made by dissolving SiO₂ in some really nasty acids and then flashing the acids off. What's left looks like a semi-solid fog. My old boss used to joke that it has "negative weight." You could keep scooping the stuff onto a scale for quite some time before you got much of any reading at all. There was no resistance to the scoop. It was like scooping fog out of a bottle. I think the trade name was CabOSil. When you blend it in with other powders, it keeps them from caking without adding really any weight. It also acts as a great thickening agent in oils and sauces or soups. Who would have guessed? (I often put a little roux of butter, flour, and cream into my recipes as a thickener, but the SiO₂ foam would have fewer calories. On the other hand, the roux does add to the flavor. /rap) As you pointed out in your column, SiO₂ is a marvelous material and is very useful in its many forms.

• Steve Krueger
• Pease: It sure does help maintain our beaches! Where would our seashores be without it?

Hi Bob: Regarding your article on SiO₂—wow, finally. It has interested me that in the areas of food, drugs, and electronics, the role of passive components often is ignored. If something is nutritive or electrically conductive, volumes are written. Yet the passive components often are either barely mentioned or ignored. (We can stop worrying about SiO₂ because it is soooo good! /rap) Almost everything electronic—ICs, transistors, capacitors, resistors, battery cells, whatever—has a certain amount of conductors. Yet none of these would work without non-conductors (insulators) or at least dielectrics. (For sure, and SiO₂ is one of the best. It has very low leakage when used to isolate input nodes, often better than 10¹⁵Ω, perhaps better than 10²⁰Ω-cm—low leakage when used in capacitors and low dielectric absorption too! Maybe not quite as good as air... /rap) In most (all?) electronic components, insulating material occupies more space, or area, or volume than conductors. (Maybe not in rectifiers... /rap) One of the most common non-conductors (or low conductors) is SiO₂. Although sand is rarely pure SiO₂ in the natural state (most sand grains also contain a wide variety of other elements and compounds, such as the conductor aluminum), SiO₂ is probably the most common major component. Yet slightly inland Silicon Valley isn't called that because of its beaches (or relative lack thereof). Your column mentions silicon as one of the components mentioned in the ingredients of various food products. This, of course, is an FDA requirement. Golly gee, there doesn't appear to be any government organization that requires such detailed listing of the components used in transistors, etc. (Such as arsenic... /rap) As long as you don't eat it, any such listing is entirely voluntary on the part of the manufacturer. When people start eating ICs, this situation may change. Chickens frequently eat sand. SiO₂ has little, if any, nutritive value. But chickens don't have any teeth. Sand grains serve as an abrasive material that breaks down other things they eat. Although SiO₂ passes through their bodies almost unchanged, it serves a useful mechanical function. (When I was a kid, we fed our chickens calcium carbonate in the form of crushed shell fragments. That was designed to work much better than sand. /rap) This whole subject really should be explored more thoroughly, especially in regard to electronics. Certainly, insulators (those things that do conduct electricity, but just barely), like air, are very useful. If you're working with very sensitive components or transmission items, like video, you don't want to wrap your ac lines around video cables, even if they're shielded, securely grounded, and insulated with a half-inch of rubber. (Next time I am running video, I will wrap some ac power lines around them and see if I can tell any difference. /rap) Yeah, a sandbox can do surprising wonders, but even this is imperfect.

• John Rupkalvis
• Pease: Thanks for the comments. Best regards.

Hello Bob: Your columns are sometimes amusing, but when will you finally switch to the metric system as used throughout Europe? (Maybe when we get worldwide cooling. Do you happen to know the schedule for Hell freezing over? That is about when I will change over entirely. When driving in Germany or France, I think in kilometers and kilometers per hour. But even there when somebody asks me "How long is your foot?" I say it is about 1 foot long, or 1.1 feet with my shoe on. The reason we think in feet is because a foot is a useful measure. /rap) Your columns about your bicycle treks only use feet. Do you prefer to use old units in electronics as well? (I could use AB-volts and STAT-volts, but those are a little too obscure. But I suppose I could start using them... /rap) How old-minded would that be?

• Istvan Cocron
• Pease: About 65 years. Even in England, many older people don't like using the metric system. An old man in England wouldn't buy a kilogram of meat or half a kilogram. He would buy 454 grams because that is what he needs. And he would certainly buy a pint of beer. When Hell freezes over, and the beer does too, then we'll consider changing.

Comments invited! rap@galaxy.nsc.com —or: Mail Stop D2597A, National Semiconductor P.O. Box 58090, Santa Clara, CA 95052-8090