PHYSIOLOGICAL  EXHAUSTION  OF  BEER  YEAST,  ETC.  163 
yeast,  yield  to  cold  water  less  than  1  decigramme  of  phosphoric 
acid. 
280  grammes  of  this  same  washed  yeast,  containing  48*2  gr. 
of  yeast  dried  at  100°,  Avere  introduced  into  a  special  apparatus 
with  1600  cubic  centimetres  of  water  boiled  and  then  cooled  to 
40°  in  a  current  of  carbonic  acid.  To  make  perfectly  sure  that 
no  foreign  bodies  were  formed,  a  few  drops  of  creosote  were 
added  to  the  water  intended  for  washing.  Every  twenty-four 
hours  the  water  was  decanted  and  fenewed  by  a  fresh  supply, 
,  under  the  same  coifditions.  All  these  washings  were  screened 
from  the  air  in  an  atmosphere  of  carbonic  acid,  the  apparatus 
being  in  a  warm  place,  the  temperature  of  Avhich  could  vary  from 
20  to  30°. 
These  washings  furnished  the  following  results  : — 
1st  washing — anhydrous  phosphoric  acid.  .  0*056 
2d  "  "  "  .  .  0-073 
3d  "  "  "  .  0-074 
4th  "  "  "  .  0-076 
5th  "  "  "  .  0-346 
6th  "  "  "  .  0-444 
7th  "  "  "  .  .  0-371 
8th  "  "  "  ,  .     .  0-190 
Total  of  phosphoric  acid     .  1*630 
These  numbers  appear  significant.  Were  beer  yeast  merely  an 
inert  precipitate,  were  phosphoric  acid  present  in  the  mass,  as 
mother  liquor  is  in  the  precipitate,  the  washings  would  eliminate 
the  greater  part  of  the  soluble  matters  in  the  first  operations,  and 
the  quantity  of  these  matters  would  diminish  more  and  more. 
But  we  see  here  that  the  yeast  at  first  resists,  then  suddenly  its 
resistance  diminishes,  and  it  yields  a  large  quantity  of  its 
disassimilated  materials.  This  is  ascertained  by  the  weight  of 
phosphoric  acid  eliminated,  which  suddenly  increases  to  five  or 
six  times  its  previous  weight ;  after  which  it  naturally  decreases. 
By  adding  the  amount  of  the  different  estimations  at  100°  of  the 
phosphoric  acid  in  dry  yeast,  the  number  will  be  found  to  be  3*38. 
The  weight  of  phosphoric  acid  eliminated  is  then  greater  by  three- 
