LEAD VALUE OF MAPLE PRODUCTS.
161I
method and its convenience in the assay of commercial almond extracts. It is probable that it could be applied also to the valuation of almond oils. MASSACHU$ETTS INSTITUTEOF TECHNOLOGY, BOSTON,MASS., August 8, 1908.
[CONTRIBUTION FROM THE
BUREAUOF
CHEMISTRY,
u. s. DEPARTMENT OF AGRICUL-
TURE. ]
THE LEAD VALUE OF MAPLE PRODUCTS. ALBERT P.SY. Received August 8, 1908.
The addition of lead subacetate or lead acetate to maple products in solution and a determination of the resulting precipitate constitutes one of the most important and most frequently used tests for purity of these products. Lead acetate when added to a pure maple product precipitates the malic and other organic acids, as well as chlorides, sulphates and carbonates, coloring and other organic matters. In cane sugar solutions this precipitation does not take place, and in maple products adulterated with cane sugar the precipitate decreases as the cane sugar increases. The lead acetate precipitation methods may be divided into four classes: first, those in which the bulk or volume of precipitate is determined-Jones,l Hortvet,2 Sy second, where the weight of the total precipitate is determined;‘ third, where the amount of acid radicals combined with the lead in the precipitate is determined, Hill and Mosher;5 fourth, in which the amount of lead in the precipitate is determined, Winton,” and the method t o be described in the following. The Lead b’alue of M a p l e Pvoducts.-Since the preliminary note? on this method, sufficient data have accumulated and satisfactory results obtained on inspection samples of maple products, so that it is thought of interest t o analysts t o give the method in detail. By “lead value” is meant the amount of lead precipitated by adding a solution of lead acetate t o IOO grams of sugar or IOO cc. of sirup. The preliminary results with this method were obtained by the following procedure: to j o grams of sugar or j o cc. of sirup about 2 0 0 cc. of water were added, the solution heated to boiling, excess of a saturated solution of lead acetate added, allowed to settle and filtered. The lead was then determined in the precipitate by the usual method, a s lead sulphate, 17th Annual RPt. Vermont Ex$. Sta.,p. 454.
* THISJOURNAL, 26, 1.532. Ibid.,Sept., 1908,p. 1429.
’ Inland
’
Revenue Dept., Ottawa, Can., Bull. 140. Tech. Quarterly, 1905, 146. THISJOURNAL, 26, 1204. J . Franklin Inst., 1906, 7 1 .
1612
;\LUERT P. S\
and calculated to P b per I O O grams o r ioo c c . So special precautions were observed as to the amount of ivater used, either for clissol\.ing the sample or washing the precipitate ; sometimes the solutions \\.ere filtered hot, sometimes cold. Ilo.ivc\.er, el-eii under tliese circ~nistances,the results obtained gave striking diirerences betiveeii pure anti atlulteratetl maple products, as will be seen from the following talde: Description of sample.
Kiiowii t o be.
Carrier sugar. . . . . . . . . . . . . . . . . Pure niaple Ranke sugar.. . . . . . . . . . . . . . . . Pure rnaplc . . . . . . . . Pure maplc . . . . . . . . Pure maple Bryant sugar.. . . . . . . . . . . . . . . . Pure maple Cooperative KO. I sugar. . . . . . . Adulterated Cooperative No. z sugar. . . . . . . Adulterated Cooperative S o . 3 s u g a r . . . . . . . Pure maple Brown sugar (cane). . . . . . . . . . . Cane sugnr Granulated sugar (cane). . , . , . , Cane sugar Maple sugar made in l a b . . . . . . . Pure maple Half maple and half cane. . . . . . Fifty per cent. maple Sirup No. 1 0 2 0 2 . . . . . . . . . . . . . Pure maple 'I No. 10203.. . . . . . . . . . . . . Adulterated '' No. 10204.. . . . . . . . . . . . . .4dultcrated '( No. 1 0 2 0 1 . . . . . . . . . . . . . . Adiilterated No. 10188.. . . . . . . . . . . . . Adulterated " iVo. 10306.. . . . . . . . . . . . . Pure mnplc No. 12130. . . . . . , . . . . . . . ildulteratetl 'I No. 1 2 2 2 1 . . . . . . . . . . . . . . Pure innple KO, 12679. . . . . . . . . . . . . . Adulterated S o . 13305.. . . . . . . . . . . . . Pure maple '' No. 13306 . . . . . . .idill terntcd ('
i(
"Lead value."
11.331 0.455 0 ,343 0 3 7,i 0.386 0.048 o ,046 '
0 . '97 0.0j2
0.006
o .429 0.21,i 0.22j
0.044 0,048 0.033 0.08.3
0.320 0.061
o 208 0.060 0.190 0.00j
Although these results show that it n-as possible to differentiate between pure and adulterated samples, it was thought desirable to so modify the method that it would gi1.e concordant results on tile same sample by the same or by different analysts. Experiments were rnade on the following points : (I) Lead Acetate f o r Precifiitation.-In all but one of the other methods known t o the writer, the basic lead acetate is used. The use of the neutral salt Lor precipitating the acid radicals present in sugars as impurities was first suggested by Blyth;' i t is also used in the Hill and Xosher method.? The advantages of the neutral over the basic lead acetate are that the former does not undergo change as quickly as the latter when exposed t o the air; its composition does not yary as does t h a t of the basic salt, the formula of the latter \-arying from I'h(OTT)C2H,0, to 'Foods, Their Composition and Anuljsis, p. I 11. 2 This method which the authors never published, is mentioned by Professor Woodman in Tech. Quarterly, 1905, 146.
1613
LEAD VALUE OF MAPLE PRODUCTS.
Pb,O,(C,H,O,),, this probably being one of the causes of the discrepaixies noticed in methods where the lead precipitate is weighed or its volume measured. The neutral salt does not precipitate caramel; it is more soluble in water and therefore more readily washed out of the precipitate than the basic salt. Basic lead acetates precipitate sugar much more readily than the neutral salt. ( 2 ) Filtering the Lead Acetate Precipitate.-The precipitate consists principally of lead malate and results as t o its solubility are reported in the following section. According to Partheil and Hiibner' the solubility of lead malate increases very much for temperatures higher than 20'. On this account the solution containing the lead precipitate should be allowed to cool, and not filtered warm, as is done in some methods. (3) bl~ashinythe Precz'pitate.-To determine the solubility of lead malate, Pb.C,H,O5.3H,0, this salt was prepared from pure malic acid and neutral lead acetate. The following results on solubility, both in water and in a 65 per cent. cane sugar sirup, were obtained: 100 cc.
Dissolved lead malate.
at aoo.
Water. . . . . . . . . . . . . . . . . . Sirup, 65 per cent.. . . . . . . .
0 . I547 0.1701
Equivalent to PbSO+
Equivalent t o Ph.
0.1193 0.1312
0.0814 0.0895
It must be remembered t h a t these results show the solubility of Pb.C4H,O,.3H,O in pure water and in a h j per cent. sirup; in the precipitation of free malic acid by lead acetate in maple products there is formed a corresponding quantity of free acetic acid in which lead malate is somewhat soluble. It becomes necessary, therefore, to use the same amount of water for each sample, both for making the solution and for washing the precipitate. The effect of different amounts of water, used for dissolving the sample, on the lead value are shown in the following table; it also shows t h a t the lead precipitate is not all lead malate, being considerably less scltihie than shown for pure lead malate in the above table; the following table also shows t h a t the solubility of the precipitate varies for different samples. Cc. water Cc. water Lead used for used for per 50 gm. dissolving. washingppt. sugar.
Maple sugar A, 50 grams.. . . . . . . . . " "
I'
"
' I I'
" "
.......... ..........
.......... Maple sugar B, 50 grams.. . . . . . . . . "
I'
"
'I
"
,'
I'
'I
...........
"Lead value."
150
100
0.270
200
IO0
250
IO0 IOO
0.254 0.234
0,540 0.508 0.468
0.200
0.400
0,385 0.348
0.770 0.696
300 150
100
200
IO0
(4) Ferrneiated S u 1 ~ ~ 5.-Occasionally le~ i t is desirable to analyze a sample t h a t has begun t o spoil or ferment. I n the early part of the work on this method, the samples were diluted and precipitated without .4rch. Pharm., 241,413.
1614
ALBERT P. SY.
being boiled, as \vats the practice in the other methods. I n some cases it )vas found that fermented, adulterated samples gave high results, producing as iiiucli lcatl 1)reciI)itate ;IS sotiie pure samples. On the supposition that the products of fermentation, especially carboii dioxide, were the cause of this, sul)seclueiit samples Lvere heated t o Iloiling before adding the leatl acetate; restilts after this \vcrc‘ in hctter agreement with facts. The fact that I I O accottiit is taken of the fermentation products, and that the samples are not I)oiletl, 110 doubt accounts for irregular results b y otlier methods, kvhere precipitation is made directly. ’l‘he following table shows the effect nil tlie results 1)). several methods on fresh and fernictitetl sani1)les: Canadian niethod. Wiriton Wt. of Pb. ppt. “Lead f r o m s g m . sample. number.”l
Adulterated sirups
No. 41 fresh.. . . . . . . . . . . . . . . . . Fermented j d a y s . . . . . . . . . . . . Fermented I O d a y s . , . . . . . . . . . . . No. 37 fresh.. . . . . . . . . . . . Fermented 14 d a y s . , . . . . . . . . . . .
.90
Volume of Lead ppt. from 5 gm.?
“Lead, value.
1.7
0. I02
..
, .
2 . 2
0.111
5.70
, .
0.126
I
.38
0.2G
3 6 I .3
I .60
0.44
2 .O
...
(6.60)
..
..
0.020
(8.9)
..
..
0,035
I
(sirup No. 26)
No. 48 fresh.. . . . . . ....... Fermented 7 days. . . . . . . . . . . . . .
At this rate of increase in values, some of these samples would soon give data corresponding t o those of pure products. These investigations finally led to adopting the following : ;llLfliotl f o r Obtcri?iiny “Lccztf L.ulitt..”--To 50 cc. of sirup or 50 grains of sugar add 2 0 0 cc. water; heat to boiling, add 20 cc. of a 10 per cent. solution of neutral lead acetate; cover, and heat again to boiling. Let stand until cold, filter and wash with water (zoo). Transfer filter and precipitate to a 400 cc. beaker, add 1.5 cc. concentrated nitric and I O cc. concentrated hydrochloric acids, cover and heat on ai1 asbestos plate, or ordinar!. hot plate; when the filter is disintegrated, remove the beaker from the plate. cool and add i o cc. of concentrated sulphuric acid; heat to fumes to expel all nitric acid. If blackening does not clear in a few minutes, carefully add 5 cc. more of nitric acid after cooling a little and again heat t o sulphuric acid funies. S o w cool, add 5 0 cc. of water, cool and add io0 cc. of alcohol; let stand six hours or over night. Filter and determine the lead sulphate, preferably by using a tared asbestos-packed Gooch, wash with alcohol, dry a n d ignite at :L low red heat. The weight of PbSO, niultiplied by 1.366 (I? X o.h83! gives the weight of lead precipitated I)!. I O U cc‘. or loo grains ol sample. ’l‘he Iccit-l w l i i c of a pure product shotild not lie less than ( ) . z ~ j o ,and is usually o \ w 0.300. The ?‘HIS JOURSAL, 2
28, 1204.
Sy, Ibid., Sept., 1908.
1615
LEAD VALUE OF MAPLE PRODUCTS.
following lead values were obtained on samples of maple sugar known to be pure. Sample No.
Lead value.
............... 2 ..................... 3 ..................... 4..................... 5 ..................... 6... . . . . . . . . . . . . . . . . . . 7 ..................... I......
8 ..................... g
.....................
0.580 0.384 0.762 0.468 0.470 0.376 (min.) 0.648 1.024(max.) 0.708 0.498
These sugars were quite dry, the average moisture content being only 3.58 per cent. The following products were made by the writer from sap; they gave “lead values” as shown: “Lead value.”
Sugar from sap of hard maple.. ..................... 0.429 Sirup from sap of hard maple.. ...................... o ,482 Sirup from sap of soft maple.. . . . . . . . . . . . . . . . . . 0.438
A complete chemical analysis of 31 samples of maple sirup bought in the open market showed t h a t 13 samples gave data for pure maple products, while 18 showed adulteration. 13 Commercial Sirufls, Pure. Minimum “Lead Value”. . . . . . . . . . . . . . . . . . “ Maximum .................. U .................. Average 18 Commercial Sirups, Adulterated. Minimum “Lead Value”. . . . . . . . . . . . . . . . . . Maximum (1 .................. Average l< ..................
o ,260 1.100
0.577
o ,024 0.165 0.076
While there is considerable variation in the lead values of pure products, due t o locality, method of manufacture, and handling, yet there is such a large difference between pure and adulterated products that there is no chance for a “doubtful” interpretation. Experience with this method has given satisfactory results, in no case “doubtful,” and in all cases concordant with the results of a complete chemical analysis. The advantages of this method are: I . The use of neutral lead acetate instead of the basic salt. 2 . A reduction of the analytical error t o a minimum, the gravimetric result being multiplied by only 2 , 50 cc. or grams of sample being taken. 3. The method is gravimetric instead of volumetric. 4. Account is taken of the solubility of the lead precipitate and the mount of water t o be used for diluting and washing is specified.
5. Error due to 1)roducts of ieriiieiitation in old or spoiled samples is avoitled 1)). boiling liefore 1irccil'it:iting. 6 . l i ' i t l i the ;ivei.qc iiioisturc coiiteiit of I O - i 2 per cent. for sugars, cciit. for sirul)s, tlie lead \-dues are in each case 011 about and >,? -3,j the same a:iioiuit oi dr!. sulistaiicc. I t might be a good plan t o make a moistlire tleteriniiiatioii on w c h sample and calculate the /cui! ziiiuc to "dr!. sulistaiice." nU1:FAI.l)
~,AI',OKATOt?T.
TYPEWRITER CARBON PAPERS. BY A .
Keceived
31. 1)oYLI:. Jline 20. 190F;.
'I'ypewriter c a r l m i papers are riiucli iisetl in the departments of the go\-ernineiit and for this reason :ti1 investigation into their qualities was made liy' the Coiitwcts 1,al)oratory oi the Bureau of Chemistry. The paper fouiiclatinii \vas tested for tensile strength, length and width ; stretch iirider straiii. 1)oth lciigth ant1 \vitith; weight, inked and clean; thickncss of inked p:tper; kiii(1 of Imlp used aiid degree of beat. ?'he i n k , as distinct from the paper, \vas separated into its coiistituents of oil or \vas, t1L-e :riitl pigiiieiits, and iiioisture and ash were determined. ,< 1 h e lvritten matter \vas rated oil ;I scale of ten aiid was also subjected t o sunlight and solul)ilit!, tests. Of the t\vciity eight samplcs esarnined, five were copy papers and the s black, blue, purple and green, all others record. Ci)p>. ~ ) q > e riiicluded of stantlard \\eight : record 1):tpers consisted of black, blue and purple : full-inketl arid s;ciiii-inketl: staiitlartl iveiglit, light weight and feather weight. 'I'ahlcs I , I I aii(1 111 represeiit the three classes of results. 111 lable I the p!i! sic:il t.ests Ii:i\e been arranged according to the weight of t h e paper, ;is tlescrilml I)!. the iii:tiiufac'turcr, while in Tables I 1 and 111 they :ire di\-itletl lii-st iiito record ~ i i i t l cup!. ; then according t o colbrblack, blue ant1 i)ii;pie, i i i tlic order iiaiiied ; :tiid finall!.) within each group a~cortliiig11, ivcxig-ht, ir0111 stmtlartl to feather weight. Discussion of Results. .I coiii1)arisoii oC tlie iigures for the \veig-lit of the paper per square centiiiieter iiitlicates that KO. 2 2 0 2 sliotild he classed with light weight papers. N o s . 2 2 0 0 , 2293, 2 2 9 4 , ? , ; o r a i r t l 2 , y ~with staiidard weight, ant1 S o s . 2 ~ 3 0 0 , 2 3 x 1 arid 2 , 3 8 2 \\.it11 tlic. light weight: I,ut otherwise these on tlie lahel of the papers> g r o i i p d :is iiit1ic;iLcd 1)) I lie ~iiaiiiifacturt.~.~ folIci~,\. c I ( w 1 ~c(>i.t;iiii \vc.iglit l i i i i i t y . Iiikctl 1xtpers average less tlixii 2 iii;:. p r s ( 1 i i : i i ~ c~ciitiiiieterf o r fe:ttlicr \veiglit, froiii 2 . 2 -?.,I llix, i o r lig-lit \\.ctig1it :iii(1 :i little less t l i a i i ;, i i i x , ior staiidarrl \\.eight. I he cleaned pa1)ws, free oi ink, ivcigh less than I iiig. for feather weight, ,%
q1.1,
, \
