public confirmPurchase(contractAddress: string, etherValue: string): Observable<string> {

    // Connect to the Contract using a Provider
    const contract: Contract = new ethers.Contract(contractAddress, this.abi, this.provider.getSigner());

    const wei = utils.parseEther(etherValue);

    // Call the contract method, getting back the transaction tx
    const token = contract.buyerConfirmPurchase({
      value: wei
    });

    return from(token)
      .pipe(
        switchMap((tx: any) => {

          console.log('buyerConfirmPurchase Tx:', tx);
          // Wait for transaction to be mined
          // Returned a Promise which would resolve to the TransactionReceipt once it is mined.
          return from(tx.wait()).pipe(
            tap((txReceipt: any) => console.log('txReceipt: ', txReceipt)),

            // The receipt will have an "events" Array, which will have
            // the emitted event from the Contract. The "PurchaseConfirmed"
            // call is the last event.
            map(txReceipt => txReceipt.events.pop()),
            tap(txEvent => console.log('event: ', txEvent.event)),
            mapTo(contractAddress),
          )
        }))
  }