20S 



NATURE 



[November 14. 1918 



into the pack, and a spring balance from which 

 the pack is hung measures the charge. The 

 receptacle is insulated hv kieselguhr, felt, 



and a final cover of leather. The insulation per- 

 mits the penetration of sufficient heat to volatilise 

 tlie li(|iii(i air at the required rate. During the 

 earlier pari ol the period of use the volume of 

 volatilised air passing out of the tube From the 

 pack is moia- than enough i" supply the wearer's 

 requirements. The current at this stage divides 

 at J (Fig. 01, one part going to tin- lungs and 

 the oilier passing low. isle through I' (the purifier) 

 and the automatic reliel valve R. The exhaled air 

 also discharges through R. Later in the period, 

 when the evaporation is less rapid, the lungs can 

 only gel the volume they call for by re-breathing 



OXYCEN 

 CYLINDERS 



•RESSURE CAUCt //VALVE 



EXKALINC VALVE, 

 REUEF VALVE 



SALIVA TRAP 



END SECTION 

 SHEWING CAUSTIC 

 30CA SPACES 



REDUONC VALVE 

 BY- CASS 



SKULL CAP 



SMOKE COCCLES 



^ NOSE CLIP 



MOUTH PIECE 



INHALINC VALVE 



a portion of the exhaled air. The flow in the 

 purifier now reverses ; the apparatus becomes a 

 regenerator, and the purifier removes the CO, 

 and moisture from that part of the expired air 

 returning to the bag. In the Newcastle model the 

 purifiei than that illustrated. An attach- 



ment i .insisting of a length of flexible 



tube ending in a mouthpiece and reliel valve. By 

 COnnei ting ube to R, it may be possible 



during tin ol a two hours' interval to 



supply air In another man. This apparatus, 

 weighing about 30 lb., is somewhat lighter than 

 most oi i 1 m pes. 



The third 1 lass oi n 1 rtus is unlike 



any of tin others. In this case the oxvgen is 

 1 . I02] 



produced, and the air regenerated, by causing the 

 products of expiration to pass through a cartridge 

 of oxylith (potassium-sodium peroxide). 'Ibis sub- 

 Stance is alt. icked by carbon dioxide and water 



V&] " with the liberation of about the same 



volume ol oxygen as the carbon dioxide and water 

 Contain. The apparatus has hitherto not been 

 successful, owing lo its excessive resistance and 

 the Ileal developed. Its small weight (about 1^ lb.) 

 is its chief ad\ anlage. 



Another interesting point brought out in the 



reporl is the necessity for the use of pure Oxygen. 



To the average man it would seem that oxygen 



showing 90 per cent, ol purity should be amply 

 sufficient for breathing purposes. One must re- 

 member, however, that in a self-contained appa- 



Fjg. 5. — Aerophor apparatus, i 



ratus the oxygen is being consumed, whereas the 



impurities — mainly nitrogen — tend to . 



for example, if a " Proto " apparatus is being 



used ill which the oxygen contains 10 per cent, of 

 nitrogen, and the wearer is doing work necessi- 

 tating the consumption of j litres of oxygen per 

 ; he "blow oft " valve not being used- 

 then after about three-quarters of an hour the 

 percentage of nitrogen in the breathing-bag will 



h.i\ e incn ed to Boil Mil., the oxygen 



being onlj u L Tht wearer persisting in 



his woiic would quickl) Income unconscious. The 

 purit) ol lie- compressed ixygen supply is there- 

 fore of great im| id the Research Com- 

 mittee lays stress 11 the necessity for having < 



