carl wilhelm scheele was associated with the discovery of oxygen.
carl wilhelm scheele was associated with the discovery of oxygen.
who is associated with the discovery of oxygen?
carl wilhelm scheele
priestley assembled his oxygen paper and several others into a second volume of "experiments and observations on air", published in 1776. he did not emphasise his discovery of "dephlogisticated air" (leaving it to part iii of the volume) but instead argued in the preface how important such discoveries were to rational religion. his paper narrated the discovery chronologically, relating the long delays between experiments and his initial puzzlements; thus, it is difficult to determine when exactly priestley "discovered" oxygen. such dating is significant as both lavoisier and swedish pharmacist carl wilhelm scheele have strong claims to the discovery of oxygen as well, scheele having been the first to isolate the gas (although he published after priestley) and lavoisier having been the first to describe it as purified "air itself entire without alteration" (that is, the first to explain oxygen without phlogiston theory).
joseph priestley
the high pressures associated with deep dives cause gases such as nitrogen to build up in tissues which are then released upon surfacing, possibly causing death. one of the ways sea lions deal with the extreme pressures is by limiting the amount of gas exchange that occurs when diving. the sea lion allows the alveoli to be compressed by the increasing water pressure thus forcing the surface air into cartilage lined airway just before the gas exchange surface. this process prevents any further oxygen exchange to the blood for muscles, requiring all muscles to be loaded with enough oxygen to last the duration of the dive. however, this shunt reduces the amount of compressed gases from entering tissues therefore reducing the risk of decompression sickness. the collapse of alveoli does not allow for any oxygen storage in the lungs however, this means that sea lions must mitigate oxygen use in order to extend their dives. oxygen availability is prolonged by the physiological control of heart rate in the sea lions. by reducing heart rate to well below surface rates, oxygen is saved by reducing gas exchange as well as reducing the energy required for a high heart rate. bradycardia is a control mechanism to allow a switch from pulmonary oxygen to oxygen stored in the muscles which is needed when the sea lions are diving to depth. another way sea lions mitigate the oxygen obtained at the surface in dives is to reduce digestion rate. digestion requires metabolic activity and therefore energy and oxygen are consumed during this process, however sea lions can limit digestion rate and decrease it by at least 54%. this reduction in digestion results in a proportional reduction in oxygen use in the stomach and therefore a correlated oxygen supply for diving. digestion rate in these sea lions increase back to normal rates immediately upon resurfacing. oxygen depletion limits dive duration, but carbon dioxide (co) build up also plays a role in the dive capabilities of many marine mammals. after a sea lion returns from a long dive, co is not expired as fast as oxygen is replenished in the blood, due to the unloading complications with co. however, having more than normal levels of co in the blood does not seem to adversely affect dive behavior. compared to terrestrial mammals, sea lions have a higher tolerance to storing co which is what normally tells mammals that they need to breathe. this ability to ignore a response to co is likely brought on by increase carotid bodies which are sensor for oxygen levels which let the animal know its available oxygen supply. yet, the sea lions cannot avoid the effects of gradual co build up which eventually causes the sea lions to spend more time at the surface after multiple repeated dives to allow for enough built up co to be expired.
sea lion