Converts pH from one scale to another one chosen between the total scale, the free scale and the seawater scale

1 |

`flag` |
choice of the type of conversion : flag=1: seawater scale to total scale flag=2: free scale to the total scale flag=3: total scale to the seawater scale flag=4: total scale to the free scale flag=5: seawater scale to the free scale flag=6: free scale to the seawater scale default is flag=1 |

`pH` |
Enter the value of pH which need to be converted, default is 8.100 |

`S` |
Salinity, default is 35 |

`T` |
Temperature in degrees Celsius, default is 25oC |

`P` |
Hydrostatic pressure in bar (surface = 0), default is 0 |

Note that the arguments can be given as a unique number or as vectors. If the lengths of the vectors are different, the longer vector is retained and only the first value of the other vectors is used. It can therefore be critical to use vectors of the same length. For instance, to compute parameters from one couple of variable for a range of temperatures, a vector with temperatures required can be given in enter and other arguments can be completed be one variable this variable will be used for each temperatures.

The function returns the values of pH converted

Héloïse Lavigne and Jean-Pierre Gattuso gattuso@obs-vlfr.fr

Dickson, A.G. & F.J. Millero, 1987 A comparison of the equilibrium constants for the dissociation of carbonic acid in seawater media. *Deep-Sea Research* **34**:1733-1743.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 | ```
##To convert pH=8.10 from the seawater scale to the total scale
##at salinity=35, temperature=25oC and atmospheric pressure:
pHc <- pHconv(flag=1, pH=8.10, S=35, T=25, P=0)
##note that pHc is the value of the pH converted in total scale
## By using vectors
## to convert the pH values : 8, 8.05, 8.10, 8.15, 8.20 from the free to the total scale
pH <- c(8, 8.05, 8.10, 8.15, 8.20)
pHc <- pHconv(flag=2, pH=pH, S=35, T=25, P=0)
##note that pHc is a vector containing the value of the pH converted in total scale
``` |

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