[USMA:36335] Re: Symbol for deka/deca

[Martin Vlietstra]

I think that the reason for using "da" as a prefix for deka was to have all prefixes up to and including "k" as lower case and prefixes from "M" and upwards as upper case.  Moreover, the prefixes "deka" and "deci" are only used in specialist applications where there is little risk of confusion.  For example, the sugar in one's blood is measured in mmol/L in the UK, but in mg/dL in Germany.  The rationale behind using mg/dL is that one need never use decimal points and need never have superfluous zeros - the normal range for a healthy person is 70 to 120 mg/dL.   As an aside, the use of mg/dL has an added advantage over mmol/L - one does not need to know the molecular weight of sugar if one wishes to calculate how much sugar a healthy adult should have in their blood stream.  Assuming that an adult has 5L of blood, then 70 mg/dL works out at 3.5g, while 120mg/dL works out at 6g - in other words about a teaspoon full.  Since I am diabetic, this information is valuable. ----- Original Message ----- From: [EMAIL PROTECTED] To: U.S. Metric Association Sent: Monday, March 20, 2006 12:33 AM Subject: [USMA:36330] Re: Symbol for deka/deca In a message dated 2006-03-19 18:54:17 Eastern Standard Time, [EMAIL PROTECTED] writes: What in the world possessed the SI committee (CGPM) to change this? D was far more consistent with the rest of the symbols for prefixes than da -- prefixes >1 are mostly capital letters, da is the ONLY prefix symbol that is not one letter. Surely there was some justification for this . . . anyone know what it was? Jim My biggest guess would be because in reality D and d where probably used interchangeably.  In the hospital I work I see many things that say ML instead of mL...It's obvious in the instances I see ML used that it means 0.001 L instead of 1000 L but with dL and DL it might not always be so obvious.   Fortunately the same hospital is trying to forbid the use of 'cc' and force the use of mL instead.  Unfortunately they also want to ban ug and enforce mcg instead.   I actually pointed out to a pharmacist that I cannot possibly administer a dose of 'one mega litre' and the dropper that says '1 ML' on the side cannot possibly contain '1 ML'.  The pharmacist looked at me like I was crazy and truly didn't understand the difference in 1 ML and 1 mL.   Richard