2017年2月24日 星期五

「養魚知識」海水比重與鹽度換算

比重的定義是「與標準物質相比的密度比值」
通常這個標準物質會定為4度C時的水(密度=1.000g/cm3) 

28度C時的水,密度為0.996g/cm3 

所以水在28度時的比重




比重不一定會以4度C時的水當作標準

一樣鹽度千分之35的標準海水,水的密度是1.022g / cm3

玻璃比重計如果準的話,量出來的比重會是1.022 

但光學比重計若以28度的水作為標準,去量同樣28度C、鹽度為千分之35的標準海水





這不代表誰準誰不準,單純是因為參考的標準不同

鹽度的定義則是「在溶液中溶有多少的鹽類」 科學上常用的單位是「重量百分濃度」或是「重量/體積濃度」(或千分濃度) 常見公式如下:

               加了多少鹽
鹽度= --------
               加了多少水

單位是g/L(重量體積濃度)或是PPT(重量千分濃度)


若海水素若是有受潮,海水素的重量會因為含水而有極大的誤差,

所以還是要用比重計驗證過比較保險

以上參考自

Re: [閒聊] 比重計,是我對不起你.
https://www.ptt.cc/bbs/Aquarium/M.1266155325.A.13D.html



以下找到一個公式,以比重在溫度下的鹽度

水溫>17.5度 :

鹽度=1035 * (比重-1) +0.3 * (溫度℃ -17.5)

水溫>17.5度 :

鹽度=1035 * (比重-1) +0.2 * (17.5-溫度)

例如在26度時,在比重1.022時,鹽度度多少?

=1305*(1.022-1)+(26-17.5)*0.3

= 31.26 PPT 

若是溫度升到30度時

=1305*(1.022-1)+(30-17.5)*0.3

32.46 PPT

溫度降到20度時


=
1305*(1.022-1)+(20-17.5)*0.3

29.46 PPT




接下來做一個表格來看一下9種溫度下的比重/鹽度變化

/℃05101517.5202530
比重鹽度鹽度鹽度鹽度鹽度鹽度鹽度鹽度
1.00155.45754.45753.45752.45751.95752.70754.20755.7075
1.00165.5884.5883.5882.5882.0882.8384.3385.838
1.0026.115.114.113.112.613.364.866.36
1.0037.4156.4155.4154.4153.9154.6656.1657.665
1.0048.727.726.725.725.225.977.478.97
1.00510.0259.0258.0257.0256.5257.2758.77510.275
1.00611.3310.339.338.337.838.5810.0811.58
1.00712.63511.63510.6359.6359.1359.88511.38512.885
1.008114.070513.070512.070511.070510.570511.320512.820514.3205
1.00915.24514.24513.24512.24511.74512.49513.99515.495
1.0116.5515.5514.5513.5513.0513.815.316.8
1.011518.507517.507516.507515.507515.007515.757517.257518.7575
1.01320.46519.46518.46517.46516.96517.71519.21520.715
1.014121.900520.900519.900518.900518.400519.150520.650522.1505
1.015223.33622.33621.33620.33619.83620.58622.08623.586
1.01624.3823.3822.3821.3820.8821.6323.1324.63
1.017125.815524.815523.815522.815522.315523.065524.565526.0655
1.018227.25126.25125.25124.25123.75124.50126.00127.501
1.018527.642526.642525.642524.642524.142524.892526.392527.8925
1.019528.947527.947526.947525.947525.447526.197527.697529.1975
1.0229.628.627.626.626.126.8528.3529.85
1.021131.035530.035529.035528.035527.535528.285529.785531.2855
1.021531.557530.557529.557528.557528.057528.807530.307531.8075
1.022232.47131.47130.47129.47128.97129.72131.22132.721
1.022933.384532.384531.384530.384529.884530.634532.134533.6345
1.023534.167533.167532.167531.167530.667531.417532.917534.4175
1.023934.689533.689532.689531.689531.189531.939533.439534.9395
1.024435.34234.34233.34232.34231.84232.59234.09235.592
1.02536.12535.12534.12533.12532.62533.37534.87536.375
1.025436.64735.64734.64733.64733.14733.89735.39736.897
1.02637.4336.4335.4334.4333.9334.6836.1837.68
1.026538.082537.082536.082535.082534.582535.332536.832538.3325
1.027138.865537.865536.865535.865535.365536.115537.615539.1155
1.02840.0439.0438.0437.0436.5437.2938.7940.29
1.028540.692539.692538.692537.692537.192537.942539.442540.9425
1.02941.34540.34539.34538.34537.84538.59540.09541.595
1.029541.997540.997539.997538.997538.497539.247540.747542.2475
1.030543.302542.302541.302540.302539.802540.552542.052543.5525
1.031544.607543.607542.607541.607541.107541.857543.357544.8575

來看一下0度~17.5度的圖表 ,我們發現愈靠近0度,相同比重的情況下,鹽度愈高。



來看一下17.5度~30度的圖表 ,發現愈靠近30度,相同比重的情況下,鹽度愈高


所以假設你在調製海水時,想要調成30%塩度,則要注意調整來源水的溫度,與缸內的

水溫溫度是否差異很大。

參考來源:


Re: [閒聊] 比重計,是我對不起你.
https://www.ptt.cc/bbs/Aquarium/M.1266155325.A.13D.html

已知海水比重1.012,温度32度,求海水盐度?问海水比重与盐度的换算公式?http://zuoye.zhishihao.com/zuoye/40950

求比重计和海水盐度的换算公式?(公式的温度有限制没?)比重计的温度使用有限制吗?
https://zhidao.baidu.com/question/358540090.html?fr=qrl&index=2&qbl=topic_question_2

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