138 
place it on a glass plate, and carefully add one drop of 10 per cent acetic 
acid. When old oil is used, a blue ring appears around the drop of acid in 
from one to five hours, whereas a freshly prepared sample remains un- 
colored for twenty-four hours or more, provided the test paper is kept 
under a bell jar to exclude laboratory fumes. This reaction is at least as 
delicate as any of the tests for rancidity based on the presence of aldehyde. 
Whether it is given by other rancid oils can not be stated at present, for I 
have as yet failed to find in the chemical literature any mention of such 
oxidizing substances in oil. The following is a table showing the reaction 
of our samples of coconut oil with fuchsin-sulphurous acid and with 
starch iodide, together with their age and acidity at the time of testing. 
For the previous history of these oils, see page 
Approxi- 7 | 
No. Reh. bl inate per Color with fuchsin-sulphurous PE cs BO | 
“ orn Tr » 9 ot. ides, 
Pe oe ae, adem 15 0.1 | Strong blues... 2-...---<:------ {8 
| ee eee ieee Coen a) | es CP 00 <i. ects ee +a 
Dee ete ot sou, w< ccnenwoe 5} 1,5 0 sree terete -- -5te } 
ee Se ee 5} AS a Sea OO 2..o (awake d- 2a ene + 
bk Ri ee 5} Bd | wendy O10 coccinea lads eke~ panne + 
Fe SS ee a Ree ee dt ef ene rs | es, eee + 
| WEEE Ne ee er pe 54 "A | Plue-reds..225-2—.5-4---.. — 
Be eS uu teseeacne 5h 2 | Btrone blues .—. <6. -- -- <> Trace, 
Te rs okies nance seks 5a US ae OD... ees cep eeele~ 28 4 
We Gate ok i Lake 5} i 06. eee. ee ew eewace -} 
re aie ee hk ennwene eee 53 i 0 <5 Ade eae ccakitiese anand + 
| nee 2a a de ee: 53 if G0 o.. siaans eee beeteeeacuen! + 
Oe ee te. acemaenaears 5 US a 0 Su. oie ihe deseo sandene + 
We Ske lbi dean uccc sawed 5 Piisiaceas 7: en = IE Oe 4 
LR: a ReneS #3 5 A 2: <n OO. 0 cee cnc aawees acene + 
1 | PRE RI Hd So ee 5 a Wo G010t 3.43 35.5055... Trace. 
Bs me oo oe oon apace 5 0.9 | Strong blue .--...-------------- + 
| | eee ee a | 5 1 SE «Pee Foe eer ey ++ 
sly (oo eS RE 4 Chin. Obici ene Se ae +: 
Tite ob PD a, eenseke d i 62]. -aheeantonawwelx. sus 4 
WO hn es bons keane d 0 emer OO scence at eee ao 
Yo as one 4 G7 | No. 0016? 22622465. { 
eh oe chicane 4 1) i ees Gj)... Se. ieee cme tae ao 
7) nk a ee 2D co 3} PG EO aM Oe ear = 
Ren codd dn oouhuneknc ane 3h 6 | Light blue-.........2.-..--- ---- ‘Trace. 
DE Ieee New ane cone sees 3h 1.5.| Strong blue.--...---...-..-.----- + 
Seek 2S a 2. eee 3} $,4 | Moderate blue_........—..------ + 
a hag in Sees 33 2.6 | Strong blue..--_--..------------ ao 
ny ME 8 Pe et Oe oe ache 3h 2.4 | Light blue___------------------- Trace, 
RN le gS a eee 3h 8.5 | Very strong blue -------------- + 
Ee a a ie eee ee ener nee 2 0:1 .| No color..-_............-.---.-=- + 
Tee eee preme eee 2 0.4 | Light blue_._------------------- + 
31 m 3} 8.5 | Tra@00. <<. -—ahn6. onsen woe + 
ro es z - 3} 7.8 | Moderate blue._.._..-..------- 
$6 Scitech 7 ee PNG AMIOE.cdbeSnaetcte =o is 
D4 pocccc ca scdacbusatecesaeseey 5a 10,2 | Strong blue -------------------- 4 
OB xh henh nal ana onncee $ 5:0 | No Glo? . cece. ee ee--..--- ot 
«Very strong. 
