维也纳标准平均海洋水（VSMOW）是科学界公认的最官方的水，其价格极为昂贵。[1] 该标准水每5毫升安瓶售价159美元，折合每加仑12万美元。[1] 之所以需要这样一种标准化的水，是因为氢和氧的不同同位素组合会影响水的物理性质，科学家需要统一的参考标准来进行精确的同位素浓度测量和温度标准化。[1]
VSMOW的制定过程跨越数年。[1] 1961年，科学家Harmon Craig在斯克里普斯海洋学研究所首次提出SMOW标准。[1] 1966年，国际原子能机构在维也纳召开会议，正式确定VSMOW作为国际计量标准。[1] 这种标准水的三相点温度为0.01℃，精度达到百万分之几度。[1] 该温度值在2019年前是国际单位制开尔文温标的定义基础，用于校准世界上最精密的温度计。[1]
Vienna Standard Mean Ocean Water (VSMOW) represents the world's most official water standard, priced at $120,000 per gallon [1]. A single 5-milliliter ampule of VSMOW costs $159, which translates to the per-gallon figure [1]. The extreme cost reflects the critical role this water plays in scientific measurement and standardization.
The need for such a precise water standard stems from the fact that different isotopic combinations of hydrogen and oxygen alter water's physical properties [1]. Scientists require a unified reference water to conduct accurate measurements of isotope concentrations and to standardize temperature measurements. The standard was first proposed in 1961 by Harmon Craig at the Scripps Institution of Oceanography [1]. The International Atomic Energy Agency formally established VSMOW as the official standard during a conference in Vienna in 1966 [1]. The triple point of VSMOW registers at 0.01 degrees Celsius with precision accurate to within a few millionths of a degree [1]. Prior to 2019, this temperature value served as the foundation for the definition of the Kelvin in the International System of Units [1].