Cochrane T T, Cochrane T A
AGTECA S.A., 230 Oceanbeach Road, Mount Maunganui, Tauranga 3116, New Zealand.
Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand.
Med Phys. 2016 Jan;43(1):225. doi: 10.1118/1.4938263.
To demonstrate that the authors' new "aqueous solution vs pure water" equation to calculate osmotic potential may be used to calculate the osmotic potentials of inorganic and organic aqueous solutions over wide ranges of solute concentrations and temperatures. Currently, the osmotic potentials of solutions used for medical purposes are calculated from equations based on the thermodynamics of the gas laws which are only accurate at low temperature and solute concentration levels. Some solutions used in medicine may need their osmotic potentials calculated more accurately to take into account solute concentrations and temperatures.
The authors experimented with their new equation for calculating the osmotic potentials of inorganic and organic aqueous solutions up to and beyond body temperatures by adjusting three of its factors; (a) the volume property of pure water, (b) the number of "free" water molecules per unit volume of solution, "Nf," and (c) the "t" factor expressing the cooperative structural relaxation time of pure water at given temperatures. Adequate information on the volume property of pure water at different temperatures is available in the literature. However, as little information on the relative densities of inorganic and organic solutions, respectively, at varying temperatures needed to calculate Nf was available, provisional equations were formulated to approximate values. Those values together with tentative t values for different temperatures chosen from values calculated by different workers were substituted into the authors' equation to demonstrate how osmotic potentials could be estimated over temperatures up to and beyond bodily temperatures.
The provisional equations formulated to calculate Nf, the number of free water molecules per unit volume of inorganic and organic solute solutions, respectively, over wide concentration ranges compared well with the calculations of Nf using recorded relative density data at 20 °C. They were subsequently used to estimate Nf values at temperatures up to and excess of body temperatures. Those values, together with t values at temperatures up to and in excess of body temperatures recorded in the literature, were substituted in the authors' equation for the provisional calculation of osmotic potentials. The calculations indicated that solution temperatures and solute concentrations have a marked effect on osmotic potentials.
Following work to measure the relative densities of aqueous solutions for the calculation of Nf values and the determination of definitive t values up to and beyond bodily temperatures, the authors' equation would enable the accurate estimations of the osmotic potentials of wide concentrations of aqueous solutions of inorganic and organic solutes over the temperature range. The study illustrates that not only solute concentrations but also temperatures have a marked effect on osmotic potentials, an observation of medical and biological significance.
证明作者新的“水溶液与纯水”方程可用于计算无机和有机水溶液在广泛的溶质浓度和温度范围内的渗透势。目前，用于医学目的的溶液的渗透势是根据基于气体定律热力学的方程计算的，这些方程仅在低温和低溶质浓度水平下才准确。医学中使用的一些溶液可能需要更准确地计算其渗透势，以考虑溶质浓度和温度。
作者通过调整方程的三个因素，对他们用于计算无机和有机水溶液渗透势的新方程进行了实验，实验温度高达并超过体温；（a）纯水的体积特性，（b）单位体积溶液中“自由”水分子的数量“Nf”，以及（c）表示给定温度下纯水协同结构弛豫时间的“t”因子。文献中可获得不同温度下纯水体积特性的充分信息。然而，由于计算Nf所需的不同温度下无机和有机溶液相对密度的信息很少，因此制定了临时方程来近似这些值。将这些值与从不同研究者计算出的值中选取的不同温度下的暂定t值代入作者的方程，以证明如何在高达并超过体温的温度范围内估算渗透势。
为计算无机和有机溶质溶液单位体积中自由水分子数量Nf而制定的临时方程，在较宽浓度范围内与使用20℃时记录的相对密度数据计算的Nf值吻合良好。随后，它们被用于估算高达并超过体温的温度下的Nf值。这些值与文献中记录的高达并超过体温的温度下的t值一起，代入作者的方程中进行渗透势的临时计算。计算结果表明，溶液温度和溶质浓度对渗透势有显著影响。
在完成测量水溶液相对密度以计算Nf值以及确定高达并超过体温的确定t值的工作后，作者的方程将能够准确估算无机和有机溶质的广泛浓度水溶液在温度范围内的渗透势。该研究表明，不仅溶质浓度，而且温度对渗透势都有显著影响，这一观察结果具有医学和生物学意义。
