The pre-biological primitive atmosphere

The primitive earth long remained covered in darkness, wrapped in dense burning clouds into which water vapor poured continuously from volcanic emissions. When temperatures finally cooled sufficiently, the clouds began to melt into rain. At first, falling on incandescent rock, the rain evaporated, but the evaporation 

It has been argued (Morse and MacKenzie 1998, Kasting and Howard 2006) that liquid water was present on parts of the earth s surface as early as 4.4 Gyr ago, i. e., within 200 million years after its formation. Water can remain as liquid up to its critical temperature (374 °C for pure water, or approximately 400 °C for  

It is a matter of speculation, without having information on the atmospheric concentrations, to assess the rainwater content. Assuming a much higher ammonia concentration than that for HCl, it is not unlikely (in contrast to the common assumption that seawater became acidic due to dissolved CO2) that in the very early earth rain and seawater were slightly alkaline. HCl is neutralized quantitatively by NH3 into NH4CI (NHJ + CI ). Possible excess NH3 reacts with dissolved CO2 and provides a buffer medium  

The continuous HCl deposition (even when taking into account a much higher level of volcanic activity in the early earth) led to acidification (remember that 

The parts of the earth s crust becoming the ocean bottom were likely to be highly alkaline because of NaO and MgO and, of much less importance, CaO (according to abundance of the cations in seawater. Table 2.9). Large amounts of soluble oxides led to dissolved Na , Mg and Ca and OH , which converts bicarbonate into less soluble carbonates (Eq. 2.30) as well as ammonium back to NH3 (Eq. 2.27) with subsequent degassing from the ocean. This is simply the explanation for the chemical composition of the seawater (Table 2.9). 

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