BaILey. | Chemistry of Gypsum. 155 
erected to manufacture the material. The crude sample ana- 
lyzed has the following composition :* 
Silicayanduincolublesresigtch eee see eee on eer AUT 
Ino ajavel alkorooinwnin, OAC obo soaandoococabdod buon ddoO 0.24 
Al CHUM O RIC SRM rece elas Meno a eels es lectotapoh aut oteliats 32.42 
Mia ome sit myo xi Gl Ome nntenn cuss evslceatien sine, sie cdo leie isis teoee sls ws 0.45 
Sulla ae Aral mola. saoladeaaooose wav MDlnenemaseee sou 44.18 
Carbonrolanmydrider(calculated)i-essemer aoe eecatn 1.67 
VV ILRPEN sees 8 boos pa RN" i SOU i OS A a SOC a 19.40 
Combining the above constituents as they probably exist in 
the crude material : 
SilicarancdensolilblesresiGucmeann rar ceeeusria icteric: Yo ALY 
Iron, are) howaMT NWA, ONCE ooo goucensodoucecoe sedobaeees 0.24 
Macnesiimecanboma tele erry reise hea evan alse. fale 0.95 
@alciunmcarnbonalepr eee Meet hoe at ee epee on aoe 2.66 
@Walcrumesullolnatenone wuss. wlan Catiehe ke cca eee Wore ees ell! 
NYVGIREN DSS yes cs Goo) et es oT Ay es EN aI OR ae ee IPRS cA oe 19.40 
LING tallereneaepene were tech iy ce ar Ne ema MENT bv 2 oie ee 100.53 
Observations upon the Composition. 
If we figure the composition of these samples from the sul- 
phuric acid, and calling pure gypsum CaSO,+2H,0, the ay- 
erage per cent. in 20 samples of gypsite from this state would 
be 79.29. There is then an average of 20.71 per cent. of im- 
purities, or substances not gypsum, in the material. 
It has been contended that the other substances in this ma- 
terial add to its value, if not present in an excessive quantity. 
This is a difficult question to settle from a chemical standpoint, 
and indeed the advantage, if any, may be mechanical rather 
than chemical. It is, however, evident from reports on the set- 
ting of those samples containing considerable calcium carbonate, 
that this material tends to defer the setting. To what extent 
does it at the same time weaken the material? If there is no. 
calcium oxide in the manufactured product, it would not seem 
probable that the action of the air would increase the hardness, 
as no carbon dioxide could be absorbed, as is the case with or- 
dinary mortar. It has not been proved, although we have made 
89. Analysis by Bailey and McFarland. 
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