April 9th, 2012 12:09pm - Posted By: Eric Brand
by Eric Brand, L.Ac.
The question of weights and measurements in Chinese medicine is complicated, and I never cease to be amazed at how few people are even aware of the complex issues around the qian. Most practitioners generally equate one Chinese qian to three grams, and we express the dose range of many common medicinals as 3-9 grams. (This dose range is based on the traditional 1-3 qian). However, the weight of one qian has varied throughout history, and most people are stunned to hear that the 3-9 gram dose ranges that we take for granted are more closely rounded to 4-11 grams in places that still use qian measurements, such as pharmacies in Hong Kong, Taiwan, Singapore, and Western Chinatowns.
Why all the confusion?
As many practitioners know, Qin Shi-huang, the first Chinese Emperor, united Chinese culture by systematizing weights, measures, and written Chinese characters during his reign from 221 to 206 BCE. The existence of a common written language and a common system of weights and measures allowed Chinese people of different regions to communicate and trade with each other, which was an unprecedented historical advantage. Even up to the present day, Chinese people that speak different dialects communicate through their use of the same common written language. (For example, Mandarin and Cantonese are mutually unintelligible when spoken, but they are written the same.) At present, the entire world outside the U.S. uses the common metric system of weights and measures, but the metric equivalent of the traditional Chinese weights is still not completely standardized.
The weight of one qian has changed numerous times throughout Chinese history. There are 10 qian in one liang, and 16 liang in one jin. From the Tang dynasty (starting in 618 CE) to the present day, the weight of one jin has been about 600 grams, making one liang about 37.5 grams and one qian about 3.75 grams. With the notable exception of classical texts such as the Jin Gui Yao Lue and the Shang Han Lun, most traditional Chinese medical texts were written during eras that used this 3.75 gram/qian measurement. Thus, if a medicinal formula from the comparatively recent Qing dynasty specified three qian of Huang Qin (Radix Scutellariae), the amount of Huang Qin that was historically used was around 11 grams, rather than the nine gram weight that most practitioners today associate with three qian.
This discrepancy exists because mainland China altered the traditional weights during a switch to the metric system in 1979, and the traditional weight units of jin-liang-qian were rounded to make the transition to the metric system smoother. Thus, the traditional 600-gram jin was rounded down to an even ½ kilogram or 500 grams. In Chinese medicine, one jin is divided into 16 liang, and each liang is divided into 10 qian. Thus, in the rounded 500 grams/jin calculation method, one liang weighs approximately 31.25 grams, and one qian weights 3.125 grams. This is the calculation method used in textbooks produced in mainland China. So the 3.125-gram qian is rounded down to three.
In mainland China, jin-liang-qian measurements are no longer commonly used for Chinese medicine. Medicinals are dosed in grams and are sold wholesale by the kilogram. Therefore, there is little practical impact of the discrepancy because the entire field is based on the metric system there. However, in Chinese communities outside of the mainland, traditional medicine practitioners often use jin-liang-qian measurements for Chinese medicine, and these overseas markets all use the 600-gram jin, 37.5-gram liang, and the 3.7-gram qian. Thus, when a doctor in Hong Kong, Taiwan, California, Amsterdam, or Seoul writes a prescription with three qian of Ren Shen (Radix Ginseng), 11 grams are dispensed, not nine grams.
The truly interesting thing is that remarkably few people are aware of this issue. Practitioners in mainland China are often amazed to hear that people still use the traditional measurements elsewhere, and people elsewhere often do not know that the 600-gram jin was rounded down to 500 grams in mainland China, creating a domino effect on all the other traditional weight units. Thus, many Western students always think of dosing medicinals in multiples of three grams, despite the fact that a multiple of four grams would be more accurate to tradition.
Making matters even more confusing, some products in China unrelated to Chinese medicine (such as tea) are still sold by the jin and liang, but based upon a different calculation method. In this calculation scheme, one jin is still an even ½ kilogram, but there are 10 liang in one jin rather than 16 liang per jin. Thus, one liang of tea or peanuts in China weighs 50 grams instead of 31.25 grams.
To summarize, one liang of tea in mainland China weighs 50 grams, and one liang of Ren Shen in China weighs 31.25 grams. In Hong Kong, Taipei, Seoul, or LA Chinatown, one liang weighs 37.3 grams, regardless of whether one is measuring tea or Ren Shen.
As complicated as this is, it is really just the tip of the iceberg in terms of measurements in Chinese medicine. Volume measurements such as the sheng are even more variable from dynasty to dynasty, and some ancient measurements are disputed up to the present day. For example, the metric equivalent of the dosages recorded in the Shang Han Lun is not definitively known.
The Shang Han Lun was written during the later half of the Han dynasty. At this time, the qian measurement was not used, but the jin and liang were both used. Thus, the precise metric weight of the Shang Han Lun liang is disputed. Some authorities suggest that the weight of one liang was close to three grams, or the modern day mainland one qian, while other authorities suggest that one liang in the Shang Han Lun times weighed about 15.68 grams, roughly equivalent to the modern day four qian (as used outside of mainland China). Other sources state approximately 13.92 grams for the Eastern Han dynasty liang.
This huge variation in metric equivalents makes modern day scholars uncertain as to whether Zhang Zhong-jing used heroic or moderate doses of medicinals. I recently had the pleasure of translating a workshop for Dr. Huang Huang, a modern master of classical formulas who was flown in from China to teach a workshop in San Francisco. There was a great turnout of experienced practitioners, and Dr. Huang delivered a fascinating four-day lecture on the Shang Han Lun and constitutional types. Dr. Huang reiterated the scholarly dispute on Zhong Zhong-jing’s dose ranges, and he tends to use a five gram per liang rule of thumb when calculating the dose of Shang Han Lun formulas. With a range of 3g-15.68 grams/liang, he feels that a five gram/liang estimate provides a conservative middle ground for estimating Shang Han Lun dose equivalents. A very interesting approach by a very thought-provoking practitioner, and it was interesting to see that even someone with decades of experience has still not been able to find a definitive answer to this fundamental question.
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