a medium consisting of sea - water is diluted to a ratio of 1 : 10 with tap - water and completed with 0 . 3 g / l of ( nh 4 ) 2 so 4 , 0 . 3 g / l kh 2 po 4 , 0 . 2 g / l k 2 hpo 4 and 2 g / l ca - formate . the ph is adjusted to 7 . 2 with ca ( oh ) 2 . the resulting substrate is inoculated with an active micro - organism from 1 % processed manure such as methanobacterium termoautotroficum and placed in a pressure - vessel with a volume of 1 l . the pressure - vessel could be stirred by a propeller . the pressure was gradually increased to 20 atm with the use of ar and was kept at that pressure at a constant temperature of + 70 ° c . the pressure was regulated by letting - out produced gas . the gas - volume produced was measured at + 70 ° c . as a function of time . the ph was kept constant by adding formic acid . measuring the ph could not be carried out inside the vessel but was carried out in sample - volumes outside the vessels and new medium was supplied to the vessel to compensate for the loss of the test volumes . for the first 24 hour - period , gas - production started very slowly but the second 24 hour - period showed very rapid gas - production . according to gas - analyses , the formed gas contained very small amounts of methane gas and mostly h 2 . this is interpreted as a microbial splitting of formic acid into co 2 and h 2 without having any following methane synthesis . when separate addition of formic acid was started still , mostly h 2 was still recorded as the gas complement but the formation of methane also started and was stabilized so that the increasing volume was 1 . 5 : 1 / 24 hour - period , which corresponds to an addition of roughly 2 g formic acid during the corresponding period . that the increasing volume during the first stage of the process is larger than that calculated probably depends on the formation of h 2 . if the added formic acid should be divided into co 2 and h 2 , the increasing volume should be 5 . 94 : 1 per 24 hour - period ( co 2 under a pressure of 20 atm is not a gas ). the same substrate and culture - equipment which was used in example 1 is now used for an experiment where the cultivation temperature was increased to + 100 ° c . the increase in volume was , before temperature increase , 1 . 4 : 1 per 24 hour - period of gas under a pressure of 20 atm . the addition of formic acid was 10 g formic acid per 24 hour - period . when the temperature was increased from + 70 ° c . to + 100 ° c ., the produced volume increased from 1 . 4 : 1 per 24 hour - period to 3 . 6 : 1 . the gas - analyses showed that the major part of this increase was due to the increased partial pressure of hydrogen . after 96 hours , the increase in volume stabilized to 2 . 3 : 1 per 24 hour - period . the temperature - increase will obviously stimulate those organisms which hydrolyze formic acid , however , organisms producing methane will not grow that fast . the ph was varied between 6 . 4 and 7 . 8 during this test . the same equipment and methods as in example 1 were started at + 35 ° c . the gas production in this experiment was slower and after 18 days a production of formic acid could be increased to 10 g per 24 - hour period . very small amounts of hydrogen were produced during this test . in fig1 is seen the accumulated change in volume with respect to time for the conditions in which 10 g per 24 hours of formic acid was added at a pressure of 20 atm and a temperature of 70 ° c .