232 



KKI'OUT OF CHKMIIAI, I,AHOHATOKY 



weak iiiucilagos. (Jmii is, for many [Hiriioscs, uscil in \vr\ strong solution, and it is highly 

 ili-sirahli' tliat a t'orni of instninifut In- ailoptcd wliicli will allow of coin|mrisoiis at the same 

 foiK'i'ntratiun. Thi' sinipli- lorm of instnuncnt tlfscrilK^d l>y Ostwald,* which is c^.-ifntially 

 that in Fig. HT, couM he inailc to answer the imrpose if the tiihe eoniieeting the two liullis lie 

 made of sullieiently large bore, A fimdy eapilliury tube will not allow the stronger solutions 

 to jiass. The determination is nnide by introdueing u known (juantity of the li(iuid at C, 

 and sueking up at I) until the liquid has risen above the mark at A. The times occupied by 

 the liijuid in (lowing from A to the lower mark at H is noted. The arrangement has the 

 advantage that the bulbs maybe submerged in water in a beaker and the temperature kept at 



Fig. 97.- Glas,s Viscosimktkk 



Dcvi-scd hy O. S. Doolittle, for 



use ill lab. of Philadelphia and 



RcidinK R.iilroad Co. 



Ton Ion 

 V'ucoiimctrr 



whatever point desired. Repeated tests can be made without alteration of temperature or 

 fear of entrance of dust — a serious matter when working at some seasons in the Sudan. 



The objection to all such funns ot' iiistruiiiciit is that tiicy arc not wholly satisfactory 

 for wide ranges of viscosity. A tube snituljjc for 3U per cent, gum solutions will be 

 coniparativelv insensitive when used to compare solutions of only 10 per cent, concentration. 

 If, however, solutions of moderate range of concentration only are to be conniared, and the 

 tube is of suitable bore the results are all that could lie desired. 



The Torsion Viscosinieter of Doolittle designed especially for the determination of 

 the viscosity of oils at varying temperatures, has been applied to gum solutions, with 

 very satisfactory results. One great advantage which the instninieiit otVers is that the 

 indications are not alTected by suspended matter unless the amount present is excessive. 



• Physico-Cliemical Mea»urciiicDt«, Ostwnld, p. 163. 



